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Filed pursuant to Rule 424(b)(3)

Registration No. 333-123371

Holding Company for United Bank

6,671,438 Shares of Common Stock

United Financial Bancorp, Inc., a federally chartered corporation, is offering for sale 6,671,438 shares of its common stock on a best efforts basis. The shares being offered represent 44.6% of the shares of common stock of United Financial Bancorp, Inc. that will be outstanding following the offering. After the offering, 53.4% of United Financial Bancorp, Inc.’s outstanding common stock will be owned by United Mutual Holding Company, our federally-chartered mutual holding company parent. United Financial Bancorp, Inc. is the holding company for United Bank. In addition, we intend to contribute cash in the amount of $150,000 and issue shares of common stock, equal to 2.0% of the shares to be outstanding following the offering, to a charitable foundation to be established by United Bank.

We must sell a minimum of 4,931,063 shares in order to complete the offering, and we will terminate the offering if we do not sell the minimum number of shares. We may sell up to 7,672,153 shares because of regulatory considerations or changes in market or economic conditions without resoliciting subscribers. The offering is scheduled to terminate at 12:00 noon, Massachusetts time, on June 20, 2005. We may extend the termination date without notice to you, until August 15, 2005, unless the Office of Thrift Supervision approves a later date, which may not be beyond May 16, 2007.

The minimum purchase is 25 shares of common stock. Generally, the maximum purchase that an individual may make through a single deposit account is 25,000 shares, and no person by himself, or with an associate or group of persons acting in concert may purchase more than 30,000 shares. For further information concerning the limitations on purchases of common stock, see “The Offering—Limitations on Purchase of Shares.” Once submitted, orders are irrevocable unless the offering is terminated or extended beyond August 15, 2005. If the offering is extended beyond August 15, 2005, subscribers will have the right to modify or rescind their purchase orders. Funds received prior to the completion of the offering will be held in an account at United Bank or, at our discretion, at another federally insured depository institution, and will bear interest at our passbook savings rate, which is currently 0.65% per annum. If the offering is terminated, subscribers will have their funds returned promptly, with interest.

Keefe, Bruyette & Woods, Inc. will use its best efforts to assist us in selling our common stock, but is not obligated to purchase any of the common stock that is being offered for sale. Subscribers will not pay any commissions to purchase shares of common stock in the offering. There is currently no public market for the common stock. Keefe, Bruyette & Woods, Inc. has advised us that it intends to make a market in the common stock, but is under no obligation to do so. We expect that the common stock of United Financial Bancorp, Inc. will be quoted on the Nasdaq National Market under the symbol “UBNK.”

This investment involves risk, including the possible loss of principal.

Please read the “ Risk Factors” beginning on page 20.

OFFERING SUMMARY

Price: $10.00 per share

These securities are not deposits or savings accounts and are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Neither the Securities and Exchange Commission, the Office of Thrift Supervision, the Federal Deposit Insurance Corporation, nor any state securities regulator has approved or disapproved these securities or has determined if this prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

KEEFE, BRUYETTE & WOODS

The date of this prospectus is May 16, 2005

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SUMMARY

The following summary explains selected information regarding the offering of common stock by United Financial Bancorp, Inc. and the business of United Bank. However, no summary can contain all the information that may be important to you. For additional information, you should read this prospectus carefully, including the consolidated financial statements and the notes to the consolidated financial statements of United Financial Bancorp, Inc.

Our Organization

In February 2004, United Bank, formerly known as United Cooperative Bank, converted its charter from a Massachusetts chartered mutual cooperative bank to a federally chartered mutual savings bank and, in April 2004, reorganized into the two-tier mutual holding company structure. As part of the reorganization, United Bank formed United Financial Bancorp, Inc. and United Mutual Holding Company, a federally chartered mid-tier stock holding company and mutual holding company, respectively. United Bank became a federally chartered capital stock savings bank, and a wholly-owned subsidiary of United Financial Bancorp, Inc., and United Financial Bancorp, Inc. became the wholly-owned subsidiary of United Mutual Holding Company. The same directors and certain officers who manage United Bank manage United Financial Bancorp, Inc. and United Mutual Holding Company.

This chart shows our current ownership structure, which is commonly referred to as the two-tier mutual holding company structure:

The Companies

United Mutual Holding Company

United Mutual Holding Company is a federally chartered mutual holding company and currently owns 100% of the outstanding shares of common stock of United Financial Bancorp, Inc. United Mutual Holding Company has not engaged in any significant business activity other than owning the common stock of United Financial Bancorp, Inc., and does not intend to expand its business activities after the offering. After the completion of the offering, United Mutual Holding Company is expected to own 53.4% of the outstanding shares of common stock of United Financial Bancorp, Inc. So long as United Mutual Holding Company exists, it will own a

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majority of the voting stock of United Financial Bancorp, Inc. The executive office of United Mutual Holding Company, is located at 95 Elm Street, West Springfield, Massachusetts 01089, and its telephone number is (413) 787-1700. United Mutual Holding Company is subject to comprehensive regulation and examination by the Office of Thrift Supervision.

United Financial Bancorp, Inc.

United Financial Bancorp, Inc. is the federally chartered mid-tier stock holding company of United Bank. As of the date of this prospectus, United Financial Bancorp, Inc. owns 100% of the common stock of United Bank and does not have any other significant assets. United Financial Bancorp, Inc. has not engaged in any significant business activity other than owning the common stock of United Bank, and does not intend to expand its business activities after the offering. United Financial Bancorp, Inc.’s executive office is located at 95 Elm Street, West Springfield, Massachusetts 01089, and its telephone number is (413) 787-1700. United Financial Bancorp, Inc. is subject to comprehensive regulation and examination by the Office of Thrift Supervision. At December 31, 2004, United Financial Bancorp, Inc. had total consolidated assets of $772.0 million, total consolidated deposits of $613.7 million and total consolidated stockholder’s equity of $62.3 million. Its net income for the year ended December 31, 2004 was $5.5 million.

United Bank

United Bank is a federally chartered savings bank headquartered in West Springfield, Massachusetts. United Bank was originally founded in 1882, as a Massachusetts-chartered cooperative bank. Over the years, United Bank has grown through internal growth as well as through a series of five mutual-to-mutual business combinations which occurred between 1960 and 1994. In February 2004, United Bank completed its conversion to a federal savings bank and, in April 2004, reorganized into the two-tier mutual holding company structure. United Bank conducts business from its main office located at 95 Elm Street, West Springfield, Massachusetts, and its ten branch offices located in Feeding Hills, Holyoke, Huntington, Indian Orchard, Longmeadow, Ludlow, Springfield and Westfield, Massachusetts. United Bank also maintains a drive-up only facility and a financial services facility which offers insurance and investment products and financial planning services, both of which facilities are located in West Springfield. The telephone number at its main office is (413) 787-1700.

United Bank’s principal business activity is the origination of mortgage loans secured by one- to four-family residential real estate, commercial real estate and commercial and industrial loans. United Bank also offers home equity loans and lines of credit, construction loans, automobile loans and other consumer loans. United Bank also invests in U.S. Government and federal agency obligations, mortgage-backed securities and other investment securities. United Bank offers a variety of deposit accounts, including demand accounts, NOW accounts, money market accounts, savings accounts, retirement accounts and certificates of deposit. Deposits are United Bank’s primary source of funds for its lending and investing activities. United Bank has also used borrowed funds as a source of funds, principally from the Federal Home Loan Bank of Boston. United Bank emphasizes exceptional personal service for its customers. United Bank is subject to comprehensive regulation and examination by the Office of Thrift Supervision.

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Business Strategy

Our business strategy is to grow and improve profitability by:

A full description of our products and services begins on page 70 of this prospectus. See also “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Business Strategy” beginning on page 52 of this prospectus for a discussion of our business strategy.

The Offering

Federal regulations require that United Mutual Holding Company own a majority of our outstanding shares of common stock. Accordingly, the shares that we are permitted to sell in the offering must represent a minority of our outstanding shares of common stock. Based on these restrictions, our Board of Directors has decided to sell 44.6% of our outstanding shares of common stock in the offering. In addition, we intend to contribute $150,000 cash and shares of common stock, equal to 2.0% of our outstanding shares of common stock following the offering, to a charitable foundation to be established by United Bank. The remaining 53.4% of our outstanding common stock will be held by United Mutual Holding Company.

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The following chart shows our structure following the offering:

United Mutual Holding Company has no plans, understandings or agreements, whether written or oral, to sell or otherwise dispose of its 53.4% of the common stock of United Financial Bancorp, Inc. However, United Mutual Holding Company may convert to stock form in the future by offering its interest in United Financial Bancorp, Inc. for sale to depositors and others in a subscription offering. United Mutual Holding Company, however, has no plans to convert to stock form.

Reasons for the Offering

The primary reasons for our decision to conduct the offering are to (1) increase our capital to support future growth and profitability, (2) compete more effectively in the financial services marketplace, and (3) offer our depositors, employees, management and directors an equity ownership interest in United Financial Bancorp, Inc. and thereby obtain an economic interest in its future success.

The capital raised in the offering is expected to:

The offering also will allow us to establish stock benefit plans for management and employees which will help us to attract and retain qualified personnel.

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Terms of the Offering

We are offering between 4,931,063 and 6,671,438 shares of common stock of United Financial Bancorp, Inc. to qualified depositors, tax-qualified employee plans and to the public to the extent shares remain available. The maximum number of shares that we sell in the offering may increase by up to 15%, to 7,672,153 shares, as a result of regulatory considerations, strong demand for the shares of common stock in the offering, or positive changes in financial markets in general and with respect to financial institution stocks in particular. Unless the estimated pro forma market value of United Financial Bancorp, Inc. decreases below $110,586,730 or increases above $172,059,950, you will not have the opportunity to change or cancel your stock order. The offering price of the shares of common stock is $10.00 per share. Keefe, Bruyette & Woods, Inc., our marketing advisor in connection with the offering, will use its best efforts to assist us in selling our shares of common stock, but Keefe, Bruyette & Woods, Inc. is not obligated to purchase any shares in the offering.

We also intend to contribute cash in the amount of $150,000 and issue shares of common stock equal to 2.0% of the shares to be outstanding following the offering, to a charitable foundation to be established by United Bank.

Persons Who May Order Stock in the Offering

We are offering the shares of common stock of United Financial Bancorp, Inc. in a “subscription offering” in the following descending order of priority:

If any shares of our common stock remain unsold in the subscription offering, we will offer such shares for sale in a community offering. Natural persons residing in Hampden and Hampshire Counties, Massachusetts, will have a purchase preference in any community offering. Shares also may be offered to the general public. The community offering, if any, may commence concurrently with, during or promptly after, the subscription offering. We also may offer shares of common stock not purchased in the subscription offering or the community offering through a syndicate of brokers in what is referred to as a syndicated community offering. The syndicated community offering, if necessary, would be managed by Keefe, Bruyette & Woods, Inc. We have the right to accept or reject, in our sole discretion, any orders received in the community offering or the syndicated community offering.

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To ensure a proper allocation of stock, each eligible account holder must list on his or her stock order form all deposit accounts in which he or she had an ownership interest at November 30, 2003, March 31, 2005 or April 30, 2005, as applicable. Failure to list an account, or providing incorrect information, could result in the loss of all or part of a subscriber’s stock allocation. We will strive to identify your ownership in all accounts, but we cannot guarantee that we will identify all accounts in which you have an ownership interest. Our interpretation of the terms and conditions of the stock issuance plan and of the acceptability of the order forms will be final.

How We Determined to Offer Between 4,931,063 Shares and 6,671,438 Shares and the $10.00 Price Per Share

The decision to offer between 4,931,063 shares and 6,671,438 shares, subject to adjustment, which is our offering range, is based on an independent appraisal of our pro forma market value prepared by RP Financial, LC., a firm experienced in appraisals of financial institutions. RP Financial, LC. is of the opinion that as of May 6, 2005, the estimated pro forma market value of the common stock of United Financial Bancorp, Inc. on a fully-converted basis was between $110,586,730 and $149,617,350, with a midpoint of $130,102,040. The term “fully converted” assumes that 100% of our common stock had been sold to the public, as opposed to the 44.6% that will be sold in the offering.

In preparing its appraisal, RP Financial, LC. considered the information contained in this prospectus, including United Financial Bancorp, Inc.’s consolidated financial statements. RP Financial, LC. also considered the following factors, among others:

In addition, we intend to contribute cash in the amount of $150,000 and issue shares of common stock, equal to 2.0% of the shares outstanding following the offering, to a charitable foundation to be established by United Bank. The intended contribution of cash and common stock to the charitable foundation has the effect of reducing our estimated pro forma valuation. See “Comparison of Valuation and Pro Forma Information with and without the Foundation.”

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In reviewing the appraisal prepared by RP Financial, LC., the Board of Directors considered the methodologies and the appropriateness of the assumptions used by RP Financial, LC. in addition to the factors listed above, and the Board of Directors believes that these assumptions were reasonable.

The Board of Directors determined that the common stock should be sold at $10.00 per share and that 44.6% of the shares of United Financial Bancorp, Inc. common stock should be offered for sale in the offering, and 53.4% should be held by United Mutual Holding Company, after giving effect to the issuance of common stock to the United Charitable Foundation. Based on the estimated valuation range and the purchase price, the number of shares of United Financial Bancorp, Inc. common stock that will be outstanding upon completion of the offering will range from 11,058,673 to 14,961,735 (subject to adjustment to 17,205,995), and the number of shares of United Financial Bancorp, Inc. common stock that will be sold in the offering will range from 4,931,063 shares to 6,671,438 shares (subject to adjustment to 7,672,153), with a midpoint of 5,801,250 shares. The number of shares that United Mutual Holding Company will own after the offering will range from 5,906,437 to 7,991,062 (subject to adjustment to 9,189,722). The number of shares of common stock that United Charitable Foundation will own after the offering will range from 221,173 to 299,235 (subject to adjustment to 344,120). The estimated valuation range may be amended with the approval of the Office of Thrift Supervision, or if necessitated by subsequent developments in the financial condition of United Bank or market conditions generally, or if permitted, to fill the order of the employee stock ownership plan.

The appraisal will be updated before we complete the offering. If the estimated pro forma market value of the common stock of United Financial Bancorp, Inc. at that time is either below $110,586,730 or above $172,059,950, then United Financial Bancorp, Inc., after consulting with the Office of Thrift Supervision, may: terminate the stock issuance plan and return all funds promptly; extend the offering or hold a new subscription or community offering, or both; establish a new offering range and commence a resolicitation of subscribers; or take such other actions as may be permitted by the Office of Thrift Supervision. Under such circumstances, we will notify you, and you will have the opportunity to change or cancel your order. In any event, the offering must be completed by no later than May 16, 2007.

Two measures investors use to analyze an issuer’s stock are the ratio of the offering price to the pro forma book value and the ratio of the offering price to the issuer’s pro forma net income. According to RP Financial, LC., while appraisers (as well as investors) use both ratios to evaluate an issuer’s stock, the price-to-book value ratio has historically been the most frequently used method due to the volatility of earnings in the thrift industry in the early- to mid-1990s and, more recently, due to decreasing interest rates. RP Financial, LC. considered these ratios, among other factors, in preparing its appraisal. Book value is the same as total equity, and represents the difference between the issuer’s assets and liabilities. The following table presents the ratio of the offering price to United Financial Bancorp, Inc.’s pro forma book value and earnings per share for the period indicated. See “Pro Forma Data” for a description of the assumptions used in making these calculations.

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Below we compare our pricing ratios to the pricing ratios of our peer group companies, i.e., the ten smallest (measured by assets) mutual holding companies whose shares trade on the Nasdaq National Market or the American Stock Exchange. The following table presents a summary of selected pricing ratios for the peer group companies and for us on a non-fully converted basis. Compared to the average pricing ratios of the peer group, our pro forma pricing ratios at the maximum of the offering range, indicated a discount of 11.1% on a price-to-earnings basis and a discount of 31.8% on a price-to-book basis. At the minimum and maximum of the valuation range, a share of common stock is priced at 19.61 times and 27.03 times our earnings. These are lower multiples than the peer group companies which, as of May 6, 2005, traded on average at 30.40 times earnings and at a median of 28.16 times earnings. At the minimum and maximum of the valuation range, the common stock is valued at 105.60% and 124.84%, respectively, of our pro forma book value. This represents a discount to the average trading price to book value of peer group companies, which as of May 6, 2005 averaged 183.15%. As of May 6, 2005, the median trading price of peer group companies was 184.74% of the book value of these companies. Consequently, a share of our common stock is less expensive than the peer group, based on an earnings per share basis and a book value per share basis.

The following table presents a summary of selected pricing ratios for the peer group companies and for us, with the ratios adjusted to the hypothetical case of being fully converted. Compared to the average fully converted pricing ratios of the peer group, our pro forma fully converted pricing ratios at the maximum of the offering range indicated a discount of 5.2% on a price-to-earnings basis and a discount of 13.4% on a price-to-book basis. At the minimum and maximum of the valuation range, a share of common stock is priced at 18.51 times and 24.52 times our earnings. At the maximum of the offering range this is a higher multiple than the peer group companies which, as of May 6, 2005, traded on average at 25.87 times earnings and at a median of 24.51 times earnings. At the minimum and maximum of the valuation range, the common stock is valued at 70.73% and 78.80%, respectively, of our pro forma book value. This

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represents a discount to the average trading price to book value of peer group companies, which as of May 6, 2005 averaged 90.96%. As of May 6, 2005, the median trading price of peer group companies was 90.12% of the book value of these companies. Consequently, at the maximum of the offering range, a share of our common stock is less expensive than the peer group on an earnings per share and on a book value per share basis. RP Financial, LC.’s calculations of the fully-converted pricing multiples for the peer group companies assume the pro forma impact of selling the mutual holding company shares of each of the peer group companies at their respective trading prices as of May 6, 2005. RP Financial, LC.’s calculation of the fully-converted pricing multiples for United Financial Bancorp, Inc. assumes the pro forma impact of selling 100% of the shares to be issued to the public at $10.00 per share.

As shown in the above tables, our pro forma fully converted and non-fully converted price-to-book value ratios are discounted compared to the average trading price to book value of the peer group companies. One reason for this discount is that 46.6% of our total outstanding shares will be owned by public stockholders, compared to an average public stock ownership percentage of 37.7% for the peer group companies. A lower public ownership percentage will result in a higher price-to-book value ratio on a non-fully converted basis.

A second reason for the price-to-book value ratio discount shown in the above tables is that if our pro forma non-fully converted price-to-book value ratio was increased to the ratio for the peer group companies, our price-to-earnings multiple would substantially exceed that of the peer group companies.

As shown in the above tables, our pro forma price-to-earnings multiple is at a premium or discount to that of the peer group companies dependent, in part, on whether our offering is assumed to be consummated at the minimum or maximum of the offering range.

The pro forma fully-converted calculations for the peer group companies include the following assumptions:

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With respect to United Financial Bancorp, Inc., the pro forma fully-converted calculations use the same assumptions as applied to the peer group companies, but also assume the impact of the establishment of our charitable foundation, the expense of the ESOP will be amortized over 20 years, and our stock option plan would be expensed over a five year period. See “Comparison of Valuation and Pro Form Information with and without the Foundation” for a discussion of the impact of our charitable foundation on our appraised value.

The independent appraisal does not indicate after-market trading value. Do not assume or expect that United Financial Bancorp, Inc.’s valuation as indicated above means that the common stock will trade at or above the $10.00 purchase price after the offering.

After-Market Performance Information

The following table presents stock price performance information for all mutual holding company initial public offerings completed between January 1, 2004 and May 6, 2005. The offerings are presented in reverse chronological order, which means that the most recent offerings appear first.

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The table above presents only short-term historical information on stock price performance, which may not be indicative of the longer-term performance of such stock prices. The data presented in the table are not intended to predict how our shares of common stock may perform following the offering. The historical information in the table may not be meaningful to you because the data were calculated using a small sample.

You should bear in mind that stock price appreciation or depreciation is affected by many factors. There can be no assurance that our stock price will not trade below $10.00 per share. As noted in the above table, six of the eight initial public offerings that closed in 2005 have traded below their initial offering price. Before you make an investment decision, we urge you to carefully read this prospectus, including, but not limited to, the section entitled “Risk Factors” beginning on page 20.

United Bank’s Officers, Directors and Employees Will Receive Additional Compensation and Benefit Programs After the Offering

We intend to establish an employee stock ownership plan, and we may implement a stock-based incentive plan that will provide for grants of stock options and restricted stock. The Board of Directors of United Bank has adopted an employee stock ownership plan, which will award shares of our common stock to eligible employees primarily based on their compensation. Our Board of Directors will, at the completion of the offering, ratify the loan to the employee stock ownership plan and the issuance of the common stock to the employee stock ownership plan. Our tax-qualified employee benefit plans, including our employee stock ownership plan, may purchase up to 10% of the shares sold in the offering (including shares issued to the United Charitable Foundation); however, it is expected that our employee stock ownership plan will purchase 8% of the shares sold in the offering and issued to the United Charitable Foundation.

In addition to shares purchased by the employee stock ownership plan, we may grant options and awards under the stock-based incentive plan. The number of options granted or shares awarded under the stock-based incentive plan may not exceed 4.90% and 1.96%, respectively, of our total outstanding shares, including shares issued to United Mutual Holding Company and to the United Charitable Foundation. The number of options granted or shares awarded under the stock-based incentive plan, when aggregated with any subsequently adopted stock-based benefit plans (exclusive of any shares held by any employee stock ownership plan), may not exceed 25% of the number of shares of common stock held by persons other than United Mutual Holding Company.

The stock-based incentive plan will comply with all applicable regulations of the Office of Thrift Supervision. The stock-based incentive plan cannot be established sooner than six months after the offering and would require the approval of our stockholders by a majority of the outstanding votes of United Financial Bancorp, Inc. eligible to be cast (excluding votes eligible to be cast by United Mutual Holding Company), unless we obtain a waiver from the Office of Thrift Supervision which would allow the approval of the stock-based benefit plan by our stockholders by a majority of votes cast (excluding shares voted by United Mutual Holding Company). We currently intend to seek such a waiver from the Office of Thrift Supervision. Unless a waiver is obtained from the Office of Thrift Supervision, the following additional Office of Thrift Supervision restrictions would apply to our stock-based incentive plan:

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In the event the Office of Thrift Supervision changes its regulations or policies regarding stock-based incentive plans, including any regulations or policies restricting the size of awards and vesting of benefits as described above, the restrictions described above may not be applicable.

The employee stock ownership plan and the stock-based incentive plan will increase our future compensation costs, thereby reducing our earnings. The Financial Accounting Standards Board (“FASB”) and the Securities and Exchange Commission recently finalized rules that require public companies to expense the grant-date fair value of stock options granted to officers, directors and employees by their first fiscal year beginning after June 15, 2005. In addition, public companies must revalue their estimated compensation costs at each subsequent reporting date and may be required to recognize additional compensation expense at those dates. Recognizing an expense equal to the grant-date fair value of stock options and any additional compensation expense due to variances in actual vesting or stock price experience compared to assumptions will increase our compensation costs over the vesting period of the options. Additionally, stockholders will experience a reduction in their ownership interest if newly issued shares of common stock are used to fund stock options and stock awards. See “Risk Factors—Our Stock-Based Incentive and Benefit Plans Will Increase Our Costs, Which Will Reduce Our Income” and “Management—Stock Benefit Plans.”

The following table summarizes the stock benefits that our officers, directors and employees may receive following the offering at the maximum of the offering range and assuming that we initially implement a stock-based incentive plan granting options to purchase 4.90% of the shares outstanding after the offering (including shares issued to the United Charitable Foundation) and awarding shares of common stock equal to 1.96% of the shares outstanding after the offering (including shares issued to the United Charitable Foundation). In the table below, it is assumed that, at the maximum of the offering range, a total of 6,671,438 shares will be sold to the public, and a total of 6,970,673 shares will be issued and outstanding to the public and the foundation. This table assumes that the Bank’s tangible regulatory capital is 10% or more following the proposed stock issuance.

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The value of the restricted shares of common stock will be based on the price of United Financial Bancorp, Inc.’s common stock at the time those shares are granted, which, subject to stockholder approval, cannot occur until at least six months after the offering. The following table presents the total value of all restricted shares to be available for award and issuance under the stock-based incentive plan, assuming the shares for the plan are purchased or issued in a range of market prices from $8.00 per share to $18.00 per share.

The grant-date fair value of the options granted under the stock-based incentive plan will be based in part on the price of United Financial Bancorp, Inc.’s common stock at the time the options are granted, which, subject to stockholder approval, cannot occur until at least six months after the offering. The value will also depend on the various assumptions utilized in estimating the value using the Black-Scholes option pricing model. The following table presents the total estimated value of the options to be available for grant under the stock option plan, assuming the market price and exercise price for the stock options are equal and the range of market prices for the shares are $8.00 per share to $18.00 per share.

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Limits on Your Purchase of Shares of Common Stock

The minimum purchase is 25 shares of common stock. Generally, no individual, or individuals through a single account, may purchase more than $250,000 (25,000 shares of common stock). If any of the following persons purchase shares of common stock, their purchases, when combined with your purchases, cannot exceed $300,000 (30,000 shares):

A detailed discussion of the limitations on purchases of common stock by an individual and persons acting together is set forth under the caption “The Offering—Limitations on Purchase of Shares.”

Subject to Office of Thrift Supervision approval, we may increase or decrease the purchase limitations in the offering at any time. In addition, in any direct community offering or syndicated community offering, we will first fill orders for our common stock up to a maximum of 1,000 shares. Thereafter, we will allocate any remaining shares of common stock on an equal number of shares per order basis, until we fill all orders. Our tax-qualified benefit plans, including our employee stock ownership plan, are authorized to purchase up to 10% of the shares sold in the offering (including shares issued to United Charitable Foundation) without regard to these purchase limitations. The employee stock ownership plan may purchase common stock in the offering, in the open market following consummation of the offering, from authorized but unissued shares of common stock, or from treasury shares following consummation of the offering.

Our Issuance of Shares of Common Stock to The Charitable Foundation

To further our commitment to our local community, we intend to establish a charitable foundation as part of the offering. We will contribute cash in the amount of $150,000 and issue shares of our common stock, ranging from 221,173 shares at the minimum of the valuation range

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to 299,235 shares at the maximum of the valuation range, which shares will have a value of $2,211,730 at the minimum of the valuation range and $2,992,350 at the maximum of the valuation range, based on the $10.00 per share offering price. As a result of the issuance of shares to the charitable foundation and the contribution of $150,000 in cash, we will record an after-tax expense of approximately $1,417,038 at the minimum of the valuation range and of approximately $1,885,410 at the maximum of the valuation range, during the quarter in which the offering is completed.

The charitable foundation will be dedicated exclusively to supporting charitable causes and community development activities in the communities in which we operate. In addition to traditional community contributions and community reinvestment initiatives, the charitable foundation will emphasize the support of education initiatives, health and human services programs, youth programs and cultural programs. In 2004 and 2003, we made $107,000 and $118,000, respectively, in charitable contributions to our community. We do not expect to discontinue our charitable contributions upon the formation of the charitable foundation. The charitable foundation is expected to make contributions totaling approximately $138,000 in its first year of operation, assuming we sell our common stock at the midpoint of the offering range. However, the charitable foundation is not expected to limit the size of its contributions to any one program or aggregate amount in any one year.

Issuing shares of common stock to the charitable foundation will:

The establishment and funding of the charitable foundation has been approved by the Board of Directors of United Mutual Holding Company.

See “Risk Factors—The Contribution of Shares to the Charitable Foundation Will Dilute Your Ownership Interests and Adversely Affect Net Income in Fiscal 2005,” “Comparison of Valuation and Pro Forma Information With and Without the Foundation” and “United Charitable Foundation.”

How You May Pay for Your Shares

In the subscription offering and the community offering you may pay for your shares only by:

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If you wish to use your United Bank individual retirement account to pay for your shares, please be aware that federal law requires that such funds first be transferred to a self-directed retirement account with a trustee other than United Bank. The transfer of such funds to a new trustee takes time, so please make arrangements as soon as possible or contact the Stock Information Center for further information. Also, please be aware that United Bank is not permitted to lend funds to anyone for the purpose of purchasing shares of common stock in the offering.

You can subscribe for shares of common stock in the offering by delivering to United Bank a signed and completed original stock order form, together with full payment, provided we receive the stock order form before the end of the offering. Payments received by United Bank will be placed in a segregated savings account or, at our discretion, another insured depository institution. We will pay interest at United Bank’s passbook rate, currently 0.65% per annum, from the date funds are received until completion or termination of the offering. Withdrawals from certificates of deposit at United Bank for the purpose of purchasing common stock in the offering may be made without incurring an early withdrawal penalty. All funds authorized for withdrawal from deposit accounts with United Bank must be in the deposit accounts at the time the stock order form is received. However, funds will not be withdrawn from the accounts until the offering is completed and will continue to earn interest at the applicable deposit account rate until the completion of the offering. A hold will be placed on those funds when your stock order is received, making the designated funds unavailable to you. After we receive an order, the order cannot be revoked or changed, except with our consent. Payment may not be made by wire transfer or any other electronic transfer of funds. In addition, we are not required to accept copies or facsimiles of order forms.

For a further discussion regarding the stock ordering procedures, see “The Offering—Prospectus Delivery and Procedure for Purchasing Shares” on page 138.

You May Not Sell or Transfer Your Subscription Rights

If you order shares of common stock in the subscription offering, you will be required to state that you are purchasing the shares of common stock for yourself and that you have no agreement or understanding to sell or transfer your subscription rights. We intend to take legal action, including reporting persons to federal or state regulatory agencies, against anyone who we believe sells or in any way transfers his or her subscription rights. We will not accept your stock order if we have reason to believe that you sold or transferred your subscription rights. In addition, joint stock registration will only be allowed if the qualified account is so registered.

Deadline for Orders of Common Stock

If you wish to purchase shares of common stock, we must receive, not simply have post-marked, your properly completed stock order form, together with payment for the shares, no later than 12:00 noon, Massachusetts time, on June 20, 2005, unless we extend this deadline. You may submit your stock order form by mail using the return envelope provided, by overnight courier to the indicated address on the stock order form, or by bringing your stock order form to our main office.

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Termination of the Offering

The subscription offering will terminate at 12:00 noon, Massachusetts time, on June 20, 2005. We expect that the community offering would terminate at the same time. We may extend this expiration date without notice to you, until August 15, 2005, unless regulators approve a later date. If the subscription offering and/or community offerings extend beyond August 15, 2005, we will be required to resolicit subscriptions before proceeding with the offering. In such event, if you choose not to subscribe for the common stock, your funds will be promptly returned to you with interest. All further extensions, in the aggregate, may not last beyond May 16, 2007.

Steps We May Take If We Do Not Receive Orders for the Minimum Number of Shares

If we do not receive orders for at least 4,931,063 shares of common stock, we may take several steps in order to sell the minimum number of shares of common stock in the offering range. Specifically, we may (i) increase the maximum number of shares that may be purchased by any subscriber (including our subscribing directors and officers) and/or (ii) seek regulatory approval to extend the offering beyond the August 15, 2005 expiration date, provided that any such extension will require us to resolicit subscriptions received in the offering.

Our Policy Regarding Dividends

Following completion of the offering, our Board of Directors will have the authority to declare dividends on our common stock, subject to statutory and regulatory requirements. While our Board of Directors currently intends to declare dividends, it has not yet determined the amount and timing of any dividend payments. The payment and amount of any dividend payments will depend upon a number of factors, including the following:

Market for the Common Stock

We anticipate that the common stock sold in the offering will be quoted on the Nasdaq National Market under the symbol “UBNK.” Keefe, Bruyette & Woods, Inc. currently intends to make a market in the shares of common stock, but it is under no obligation to do so.

How We Intend to Use the Proceeds We Raise from the Offering

Assuming we sell 6,671,438 shares of common stock in the offering, and we have net proceeds of $65.1 million, we intend to distribute the net proceeds as follows:

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We may use the net proceeds of the offering to invest in securities, to deposit funds in United Bank, to finance the possible acquisition of other financial institutions or financial service businesses, to pay dividends or for other general corporate purposes, including repurchasing shares of our common stock. United Bank may use the proceeds it receives to make loans, to purchase securities, to expand its banking franchise internally, through branching or through acquisitions, and for general corporate purposes. See “How We Intend to Use the Proceeds from the Offering.” Neither United Bank nor United Financial Bancorp, Inc. is considering any specific material acquisition transaction at this time.

Tax Consequences of the Offering

The offering will result in no taxable gain or loss to United Mutual Holding Company, United Financial Bancorp, Inc. or United Bank, or to depositors who have a priority right to subscribe for shares of common stock in the offering, or to our employees, officers or directors, except to the extent that the nontransferable subscription rights to purchase shares of common stock in the offering may be determined to have value. Luse Gorman Pomerenk & Schick, P.C. has opined as to federal law that it is more likely than not that the fair market value of such subscription rights is zero. In that case, no taxable gain or loss will need to be recognized by depositors who receive nontransferable subscription rights. We discuss these matters in greater detail at page 133 of this prospectus.

Once Submitted, Your Purchase Order May Not Be Revoked Unless the Offering is Terminated or Extended Beyond August 15, 2005.

Funds that you use to purchase shares of our common stock in the offering will be held in an interest-bearing account until the termination or completion of the offering, including any extension of the expiration date. The Office of Thrift Supervision approved the offering on May 16, 2005; however, because completion of the offering will be subject to an update of the independent appraisal, among other factors, there may be one or more delays in the completion of the reorganization. Any orders that you submit to purchase shares of our common stock in the offering are irrevocable, and you will not have access to subscription funds unless the offering is terminated, or extended beyond August 15, 2005.

Restrictions on the Acquisition of United Financial Bancorp, Inc. and United Bank

Federal regulations, as well as provisions contained in the charter and bylaws of United Bank, restrict the ability of any person, firm or entity to acquire United Financial Bancorp, Inc., United Bank, or their respective capital stock. These restrictions include the requirement that a potential acquirer of common stock obtain the prior approval of the Office of Thrift Supervision

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before acquiring in excess of 10% of the stock of United Financial Bancorp, Inc. or United Bank. Because a majority of the shares of outstanding common stock of United Financial Bancorp, Inc. must be owned by United Mutual Holding Company, any acquisition of United Financial Bancorp, Inc. must be approved by United Mutual Holding Company, and United Mutual Holding Company would not be required to pursue or approve a sale of United Financial Bancorp, Inc. even if such sale were favored by a majority of United Financial Bancorp, Inc.’s public stockholders.

Possible Conversion of United Mutual Holding Company to Stock Form

In the future, United Mutual Holding Company may convert from the mutual to capital stock form in a transaction commonly known as a “second-step conversion.” In a second-step conversion, depositors of United Bank would have subscription rights to purchase common stock of United Financial Bancorp, Inc. or its successor, and the public stockholders of United Financial Bancorp, Inc. would be entitled to exchange their shares of common stock for an equal percentage of shares of the stock holding company resulting from the conversion. This percentage may be adjusted to reflect any assets owned by United Mutual Holding Company. United Financial Bancorp, Inc.’s public stockholders, therefore, would own approximately the same percentage of the resulting stock holding company as they owned prior to the second-step conversion.

The Board of Directors has no current plan to undertake a second-step conversion transaction. Any second-step conversion transaction would require the approval of holders of a majority of the outstanding shares of United Financial Bancorp, Inc. common stock (excluding shares held by United Mutual Holding Company) and the approval of a majority of the votes held by depositors of United Bank, with depositors entitled to cast one vote per $100 on deposit at United Bank (up to a maximum of 1,000 votes).

Proposed Stock Purchases by Management

United Financial Bancorp, Inc.’s directors and executive officers and their associates are expected to purchase approximately 157,000 shares of common stock in the offering, which represents 2.71% of the shares sold to the public and 1.21% of the total shares to be outstanding after the offering at the midpoint of the offering range. Directors and executive officers will pay the same $10.00 per share price paid by all other persons who purchase shares in the offering. These shares will be counted in determining whether the minimum of the range of the offering is reached.

How You May Obtain Additional Information Regarding the Offering

If you have any questions regarding the offering, please call the Stock Information Center at (413) 788-3333, Monday through Friday between 8:30 a.m. and 4:00 p.m., Massachusetts time. The Stock Information Center is located at our main office at 95 Elm Street, West Springfield, Massachusetts 01089.

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RISK FACTORS

You should consider carefully the following risk factors in evaluating an investment in the

common stock.

Risks Related to Our Business

Future Changes in Interest Rates Could Reduce Our Profits

Our ability to make a profit largely depends on our net interest income, which could be negatively affected by changes in interest rates. Net interest income is the difference between:

The rates we earn on our assets and the rates we pay on our liabilities are generally fixed for a contractual period of time. Like many savings institutions, our liabilities generally have shorter contractual maturities than our assets. This imbalance can create significant earnings volatility, because market interest rates change over time. In a period of rising interest rates, the interest income earned on our assets may not increase as rapidly as the interest paid on our liabilities. In a period of declining interest rates, the interest income earned on our assets may decrease more rapidly than the interest paid on our liabilities, as borrowers prepay mortgage loans, and mortgage-backed securities and callable investment securities are called or prepaid thereby requiring us to reinvest those cash flows at lower interest rates. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations — Management of Market Risk” on page 61.

In addition, changes in interest rates can affect the average life of loans and mortgage-backed and related securities. A reduction in interest rates results in increased prepayments of loans and mortgage-backed and related securities, as borrowers refinance their debt in order to reduce their borrowing costs. This creates reinvestment risk, which is the risk that we may not be able to reinvest prepayments at rates that are comparable to the rates we earned on the prepaid loans or securities. Additionally, increases in interest rates may decrease loan demand and/or make it more difficult for borrowers to repay adjustable rate loans.

As of December 31, 2004, we were servicing loans sold to third parties totaling $52.2 million, and the mortgage servicing rights associated with such loans had a book value, at such date, of $199,000. Generally, the value of mortgage servicing rights increases as interest rates rise and decreases as interest rates fall, because the estimated life and estimated income from the underlying loans increase with rising interest rates and decrease with falling interest rates.

Changes in interest rates also affect the current market value of our interest-earning securities portfolio. Generally, the value of securities moves inversely with changes in interest rates. At December 31, 2004, the fair value of our agency securities, mortgage-backed securities

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and corporate debt obligations, all classified as available for sale, totaled $152.1 million. Unrealized net losses on these available-for-sale securities totaled $700,000 at December 31, 2004 and are reported as a separate component of stockholder’s equity. Further decreases in the fair value of securities available for sale in future periods would have an adverse effect on stockholder’s equity.

We evaluate interest rate sensitivity using a model prepared by the Office of Thrift Supervision that estimates the change in United Bank’s net portfolio value over a range of interest rate scenarios. Net portfolio value is the discounted present value of expected cash flows from assets, liabilities and off-balance sheet contracts. At December 31, 2004, in the event of an immediate 200 basis point increase in interest rates, the model projects that we would experience a $20.9 million, or 24.0%, decrease in net portfolio value. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations — Management of Market Risk” on page 61.

Because We Intend to Increase Our Commercial Real Estate and Commercial and Industrial Loan Originations, Our Lending Risk Will Increase and Downturns in the Real Estate Market or Local Economy Could Adversely Affect Our Earnings.

At December 31, 2004, our portfolio of commercial real estate loans totaled $137.8 million, or 24.0% of our total loans, and our portfolio of commercial and industrial loans totaled $56.3 million, or 9.8% of our total loans. These loans have increased as a percentage of our total loan portfolio in recent years. These loans generally have more risk than one-to four-family residential mortgage loans. Because the repayment of commercial real estate and commercial and industrial loans depends on the successful management and operation of the borrower’s properties or related businesses, repayment of such loans can be affected by adverse conditions in the real estate market or the local economy. Many of our borrowers also have more than one commercial real estate or commercial and industrial loan outstanding with us. Consequently, an adverse development with respect to one loan or one credit relationship can expose us to significantly greater risk of loss compared to an adverse development with respect to a one- to four-family residential mortgage loan. Finally, if we foreclose on a commercial real estate or commercial and industrial loan, our holding period for the collateral, if any, typically is longer than for one- to four-family residential mortgage loans because there are fewer potential purchasers of the collateral. Because we plan to continue to increase our originations of these loans, it may be necessary to increase the level of our allowance for loan losses because of the increased risk characteristics associated with these types of loans. Any such increase to our allowance for loan losses would adversely affect our earnings.

If Economic Conditions Deteriorate, Our Results of Operations and Financial Condition Could Be Adversely Affected as Borrowers’ Ability to Repay Loans Declines and the Value of the Collateral Securing Our Loans Decreases.

Our financial results may be adversely affected by changes in prevailing economic conditions, including decreases in real estate values, changes in interest rates which may cause a decrease in interest rate spreads, adverse employment conditions, the monetary and fiscal policies of the federal government and other significant external events. Particularly, in recent years, the prices of real estate have significantly increased in our market area. Because we

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originate a significant number of mortgage loans secured by residential real estate, decreases in real estate values could adversely affect the value of property used as collateral for such loans. At December 31, 2004, loans secured by residential real estate, including home equity loans and lines of credit, represented 57.6% of our total loans. Adverse changes in the economy also may have a negative effect on the ability of our borrowers to make timely repayments of their loans, which would have an adverse impact on our earnings. As of December 31, 2004, the unemployment rates in Hampden and Hampshire Counties, Massachusetts were 5.0% and 3.0%, respectively, which were lower than the national average of 5.1%. At that same date, the Massachusetts unemployment rate was 4.1%.

Strong Competition Within Our Market Area May Limit Our Growth and Profitability.

Competition in the banking and financial services industry is intense. In our market area, we compete with commercial banks, savings and cooperative institutions, mortgage brokerage firms, credit unions, finance companies, mutual funds, insurance companies, and brokerage and investment banking firms operating locally and elsewhere. Recently, the largest regional financial institution in our market area agreed to be acquired by a substantially larger money-center bank, which we expect will increase competition in our market area. Some of our competitors have substantially greater resources and lending limits than we have, have greater name recognition and market presence that benefit them in attracting business, and offer certain services that we do not or cannot provide. In addition, larger competitors may be able to price loans and deposits more aggressively than we do. Our profitability depends upon our continued ability to successfully compete in our market area. The greater resources and deposit and loan products offered by some of our competitors may limit our ability to increase our interest-earning assets. For additional information see “Business of United Bank—Competition.”

If Our Allowance for Loan Losses is Not Sufficient to Cover Actual Loan Losses, Our Earnings Could Decrease.

We make various assumptions and judgments about the collectibility of our loan portfolio, including the creditworthiness of our borrowers and the value of the real estate and other assets serving as collateral for the repayment of many of our loans. In determining the amount of the allowance for loan losses, we review our loans and our loss and delinquency experience, and we evaluate economic conditions. If our assumptions are incorrect, our allowance for loan losses may not be sufficient to cover losses inherent in our loan portfolio, resulting in additions to our allowance. While our allowance for loan losses was 1.0% of total loans and 152.0% of non-performing loans at December 31, 2004, both higher than our peer group of financial institutions, material additions to our allowance could materially decrease our net income.

In addition, bank regulators periodically review our allowance for loan losses and may require us to increase our provision for loan losses or recognize further loan charge-offs. Any increase in our allowance for loan losses or loan charge-offs as required by these regulatory authorities may have a material adverse effect on our financial condition and results of operations.

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Risks Related to the Offering

The Future Price of the Common Stock May Be Less Than the Purchase Price in the Offering.

We cannot assure you that if you purchase shares of common stock in the offering you will later be able to sell them at or above the purchase price in the offering. In several cases, shares of common stock issued by newly converted savings institutions or mutual holding companies have traded below the price at which such shares were sold in the offering conducted by those companies. The final aggregate purchase price of the shares of common stock in the offering will be based on an independent appraisal. The appraisal is not intended, and should not be construed, as a recommendation of any kind as to the advisability of purchasing shares of common stock. The valuation is based on estimates and projections of a number of matters, all of which are subject to change from time to time. After our shares begin trading, the trading price of our common stock will be determined by the marketplace, and may be influenced by many factors, including prevailing interest rates, the overall performance of the economy, investor perceptions of United Financial Bancorp, Inc. and the outlook for the financial institutions industry in general.

There May be a Limited Trading Market in Our Common Stock, Which May Hinder Your Ability to Sell Our Common Stock and May Lower the Market Price of the Stock.

United Financial Bancorp, Inc. has never issued common stock and, therefore, there is no current trading market for the shares of common stock. We expect that our common stock will be quoted on the Nasdaq National Market. It is possible that an active and liquid trading market in shares of our common stock will not develop. Persons purchasing shares may not be able to sell their shares when they desire if a liquid trading market does not develop or sell them at a price equal to or above the initial purchase price of $10.00 per share even if a liquid trading market develops. This limited trading market for our common stock may reduce the market value of the common stock and make it difficult to buy or sell our shares on short notice. For additional information see “Market for the Common Stock.”

Our Return on Equity Will Be Low Compared to Other Financial Institutions. This Could Negatively Affect the Trading Price of Our Common Stock.

Net income divided by average equity, known as “return on equity,” is a ratio many investors use to compare the performance of a financial institution to its peers. For the year ended December 31, 2004, our return on average equity was 9.25%, compared to a return on average equity of 8.43% for all publicly traded savings institutions. Following the offering, we expect our consolidated equity to increase from $62.3 million to between $104.6 million at the minimum and $128.8 million at the adjusted maximum of the offering range. We expect our return on equity to remain below the industry average until we are able to leverage the additional capital we receive from the offering. Our return on equity will be reduced by the capital raised in the offering, higher expenses from the costs of being a public company, and added expenses associated with our employee stock ownership plan and the stock-based incentive plan we intend to adopt. Until we can increase our net interest income and non-interest income, we expect our return on equity to be below the industry average, which may reduce the value of our common stock.

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The Contribution of Shares to the Charitable Foundation Will Dilute Your Ownership Interests and Adversely Affect Net Income in Fiscal 2005.

We intend to establish a charitable foundation in connection with the offering. We will make a contribution to the charitable foundation in the form of shares of United Financial Bancorp, Inc. common stock and $150,000 in cash. At the midpoint of the offering range, we will contribute 260,204 shares of common stock to the charitable foundation, which equals 2.0% of the shares of common stock outstanding following the offering. The aggregate contribution will also have an adverse effect on our net income for the quarter and year in which we make the issuance and contribution to the charitable foundation. The after-tax expense of the contribution will reduce net income in our 2005 fiscal year by approximately $1,651,224 at the midpoint of the offering range. Persons purchasing shares in the offering will have their ownership and voting interests in United Financial Bancorp, Inc. diluted by 2.0% due to the issuance of shares of common stock to the charitable foundation.

Our Contribution to the Charitable Foundation May Not Be Tax Deductible, Which Could Reduce Our Profits.

We believe that the contribution to United Charitable Foundation will be deductible for federal income tax purposes. However, we cannot assure you that the Internal Revenue Service will grant tax-exempt status to the charitable foundation. If the contribution is not deductible, we would not receive any tax benefit from the contribution. In addition, even if the contribution is tax deductible, we may not have sufficient profits to be able to use the deduction fully.

Our Stock-Based Incentive and Benefit Plans Will Increase Our Costs, Which Will Reduce Our Income.

We anticipate that our employee stock ownership plan will purchase 8% of the shares of common stock sold in the offering and issued to United Charitable Foundation with funds borrowed from United Financial Bancorp, Inc. The cost of acquiring the shares of common stock for the employee stock ownership plan will be between $4,121,790 at the minimum of the offering range and $6,413,020 at the adjusted maximum of the offering range. We will record annual employee stock ownership plan expenses in an amount equal to the fair value of shares of common stock committed to be released to employees. If shares of common stock appreciate in value over time, compensation expense relating to the employee stock ownership plan will increase.

We also intend to adopt a stock-based incentive plan after the offering under which plan participants would be awarded shares of our common stock (at no cost to them) or options to purchase shares of our common stock. Under Office of Thrift Supervision regulations, we are authorized to grant awards of stocks or options under one or more stock-based incentive plans, in an amount up to 25% of the number of shares of common stock held by persons other than United Mutual Holding Company. The number of shares of common stock or options granted under any initial stock-based incentive plan may not exceed 1.96% and 4.90%, respectively, of

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our total outstanding shares, including shares issued to United Charitable Foundation and to United Mutual Holding Company. However, if we grant additional shares of common stock or options in excess of these amounts (which grants currently would require Office of Thrift Supervision non-objection) such grants would increase our costs further.

The shares of common stock granted under the stock-based incentive plan will be expensed by us over their vesting period at the fair market value of the shares on the date they are awarded. (These stock grants or awards are sometimes referred to in this prospectus and pro forma data tables as shares awarded under our recognition and retention plan.) If the shares of common stock to be granted under the plan are repurchased in the open market (rather than issued directly from authorized but unissued shares by United Financial Bancorp, Inc.) and cost the same as the purchase price in the offering, the reduction to stockholders’ equity due to the plan would be between $2,167,500 at the minimum of the offering range and $3,372,370 at the adjusted maximum of the offering range. To the extent we repurchase shares of common stock in the open market to fund the grants of shares under the plan, and the price of such shares exceeds the offering price of $10.00 per share, the reduction to stockholders’ equity would exceed the range described above. Conversely, to the extent the price of such shares is below the offering price of $10.00 per share, the reduction to stockholders’ equity would be less than the range described above.

Finally, new accounting rules will require public companies to recognize in the income statement the grant-date fair value of stock options, by their first fiscal year beginning after June 15, 2005. In addition, public companies must revalue their estimated compensation costs at each subsequent reporting period and may be required to recognize additional compensation expense at these dates. This could result in significant compensation and benefits expense. When we record an expense for the grant of options using the fair value method as described in the new accounting rules, we will incur significant compensation and benefits expense. As discussed in the Management’s Discussion and Analysis section of this prospectus, and based on certain assumptions discussed there, we estimate this annual expense would be approximately $658,000 on a pre-tax basis, assuming the adjusted maximum number of shares is sold in the offering.

The Implementation of Stock-Based Incentive Plans May Dilute Your Ownership Interest.

We intend to adopt a stock-based incentive plan following the offering. This stock-based incentive plan will be funded through either open market purchases, if permitted, or from the issuance of authorized but unissued shares. Stockholders would experience a reduction in ownership interest (including shares held by United Mutual Holding Company) totaling 6.4% in the event newly issued shares are used to fund stock options or awards of shares of common stock under the plan in an amount equal to 4.90% and 1.96%, respectively, of the shares issued in the offering, including shares issued to United Charitable Foundation and to United Mutual Holding Company.

We Have Broad Discretion in Using the Proceeds of the Offering. Our Failure to Effectively Use Such Proceeds Could Hurt Our Profits.

United Financial Bancorp, Inc. will use a portion of the net proceeds to finance the purchase of common stock in the offering by the employee stock ownership plan and may use

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the remaining net proceeds to pay dividends to stockholders, repurchase shares of common stock, purchase investment securities, deposit funds in United Bank, acquire other financial services companies or for other general corporate purposes. United Bank may use the proceeds it receives to fund new loans, establish or acquire new branches, purchase investment securities, or for general corporate purposes. In addition, we intend to expand our presence within and outside our primary market area through acquisitions and de novo branching, which may negatively impact our earnings until these branches achieve profitability. We have not, however, identified specific amounts of proceeds for any of these purposes and we will have significant flexibility in determining the amount of net proceeds we apply to different uses and the timing of such applications. Our failure to utilize these funds effectively could reduce our profitability. We have not established a timetable for the effective deployment of the proceeds and we cannot predict how long we will require to effectively deploy the proceeds.

Persons Who Purchase Stock in the Offering Will Own a Minority of United Financial Bancorp, Inc.’s Common Stock and Will Not Be Able to Exercise Voting Control Over Most Matters Put to a Vote of Stockholders.

Public stockholders will own a minority of the outstanding shares of United Financial Bancorp, Inc.’s common stock. As a result, stockholders other than United Mutual Holding Company will not be able to exercise voting control over most matters put to a vote of stockholders. United Mutual Holding Company will own a majority of United Financial Bancorp, Inc.’s common stock after the offering and, through its Board of Directors, will be able to exercise voting control over most matters put to a vote of stockholders. The same directors and certain officers who manage United Financial Bancorp, Inc. and United Bank also manage United Mutual Holding Company. Further, these same directors and officers are expected to purchase an aggregate of 2.71% of the shares sold at the midpoint of the offering range, thereby further reducing the voting control of public stockholders who own a minority of the outstanding shares. The only matters as to which stockholders other than United Mutual Holding Company will be able to exercise voting control include any proposal to implement a stock-based incentive plan after the completion of the offering or for a second-step stock conversion. In addition, United Mutual Holding Company may exercise its voting control to prevent a sale or merger transaction in which stockholders could receive a premium for their shares.

Our Stock Value May be Negatively Affected by Federal Regulations Restricting Takeovers and Our Mutual Holding Company Structure.

Federal Regulations Restricting Takeovers. For three years following the offering, Office of Thrift Supervision regulations prohibit any person from acquiring or offering to acquire more than 10% of our common stock without the prior written approval of the Office of Thrift Supervision. Moreover, current Office of Thrift Supervision policy prohibits the acquisition of a mutual holding company subsidiary by any person or entity other than a mutual holding company or a mutual institution. See “Restrictions on the Acquisition of United Financial Bancorp, Inc. and United Bank” on page 147 for a discussion of applicable Office of Thrift Supervision regulations regarding acquisitions.

The Mutual Holding Company Structure May Impede Takeovers. United Mutual Holding Company, as the majority stockholder of United Financial Bancorp, Inc., will be able to

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control the outcome of virtually all matters presented to stockholders for their approval, including a proposal to acquire United Financial Bancorp, Inc. Accordingly, United Mutual Holding Company may prevent the sale of control or merger of United Financial Bancorp, Inc. or its subsidiaries even if such a transaction were favored by a majority of the public stockholders of United Financial Bancorp, Inc.

The Corporate Governance Provisions in our Charter and Bylaws May Prevent or Impede the Holders of a Minority of Our Common Stock From Obtaining Representation on Our Board of Directors.

Provisions in our charter and bylaws may prevent or impede holders of a minority of our common stock from obtaining representation on our Board of Directors. For example, our Board of Directors is divided into three staggered classes. A classified board makes it more difficult for stockholders to change a majority of the directors because it generally takes at least two annual elections of directors for this to occur. Second, our charter provides that there will not be cumulative voting by stockholders for the election of our directors, which means that United Mutual Holding Company, as the holder of a majority of the shares eligible to be voted at a meeting of stockholders, may elect all of our directors to be elected at that meeting. Third, our bylaws contain procedures and timetables for a stockholder wanting to make a nomination for the election of directors or a proposal for new business at a meeting of stockholders, the effect of which may be to give our management time to solicit its own proxies in an attempt to defeat any dissident slate of nominations if management thinks it is in the best interest of stockholders generally.

Office of Thrift Supervision Policy on Remutualization Transactions Could Prohibit Acquisition of United Financial Bancorp, Inc., Which May Lower Our Stock Price.

Current Office of Thrift Supervision regulations permit a mutual holding company subsidiary to be acquired by a mutual institution or a mutual holding company in a so-called “remutualization” transaction. The possibility of a remutualization transaction and the successful completion of a small number of remutualization transactions where significant premiums have been paid to minority stockholders has resulted in some takeover speculation for mutual holding companies, which may be reflected in the per share price of mutual holding companies’ common stock. However, the Office of Thrift Supervision has issued a policy statement indicating that it views remutualization transactions as raising significant issues concerning disparate treatment of minority stockholders and the mutual interests of the mutual holding company and as raising issues concerning the effect on the mutual interests of the acquiring entity. Under certain circumstances, the Office of Thrift Supervision intends to give these issues special scrutiny and to reject applications providing for the remutualization of a mutual holding company unless the applicant can clearly demonstrate that the Office of Thrift Supervision’s concerns are not warranted in the particular case. Should the Office of Thrift Supervision prohibit or otherwise restrict these transactions in the future, our per-share stock price may be adversely affected.

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SELECTED FINANCIAL AND OTHER DATA

The summary information presented below at or for each of the fiscal years presented is derived in part from the consolidated financial statements of United Financial Bancorp, Inc. The following information is only a summary, and should be read in conjunction with our consolidated financial statements and notes beginning on page F-1 of this prospectus.

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RECENT DEVELOPMENTS

The following tables set forth certain financial and other information of United Financial Bancorp, Inc. as of the dates and periods indicated. The financial data as of December 31, 2004 has been derived in part from the audited consolidated financial statements of United Financial Bancorp, Inc. and notes thereto presented elsewhere in this prospectus. The financial data as of March 31, 2005 and 2004 and for the three-month periods then ended have been derived in part from unaudited consolidated financial statements of United Financial Bancorp, Inc. which, in the opinion of management, include all adjustments (consisting of normal recurring accruals) necessary for the fair presentation of such information. The results of operations for the three months ended March 31, 2005 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2005.

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Comparison of Financial Condition at March 31, 2005 and December 31, 2004

Total assets increased $24.0 million, or 3.1%, to $796.0 million at March 31, 2005 from $772.0 million at December 31, 2004. The increase reflected growth of $22.0 million in investment securities and mortgage-backed securities available for sale, partially offset by a $3.3 million, or 0.6%, decrease in net loans. The growth in assets was funded by a $24.4 million, or 4.0%, increase in deposits.

Net loans decreased to $565.9 million at March 31, 2005 from $569.2 million at December 31, 2004. One- to four-family residential mortgage loans increased $3.8 million, or 1.2%, to $334.7 million at March 31, 2005 from $330.8 million at December 31, 2004, reflecting continued demand in our primary market area for residential mortgage loans.

Commercial real estate loans increased $2.6 million, or 1.9%, while commercial and industrial loans decreased $5.5 million, or 9.9%. The increase in commercial real estate loans reflected our continued efforts to diversify our lending activities and improve our interest rate spread by increasing our origination of these generally higher-yielding loans. The decrease in commercial and industrial loans resulted from a payoff of a participation loan. Construction loans decreased $3.1 million, or 10.3%, to $26.8 million at March 31, 2005, reflecting completion of construction projects.

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Securities available for sale increased $22.0 million, or 14.4%, to $174.3 million at March 31, 2005 from $152.3 million at December 31, 2004. The increase reflected the deployment of funds provided by deposit growth.

Total cash and cash equivalents increased $4.6 million, or 19.6%, to $27.8 million at March 31, 2005 from $23.2 million at December 31, 2004, reflecting routine fluctuations in cash balances.

Total deposits increased $24.4 million, or 4.0%, to $638.1 million at March 31, 2005 from $613.7 million at December 31, 2004. The increase primarily reflected continued growth in certificate of deposit accounts, which increased to $224.1 million at March 31, 2005, from $204.7 million at December 31, 2004. Federal Home Loan Bank advances decreased $2.0 million, or 2.3%, to $84.7 million at March 31, 2005 from $86.7 million at December 31, 2004. The slight decrease in advances reflected the growth of deposits as our primary funding source. Repurchase agreements increased to $6.3 million at March 31, 2005 from $4.3 million at December 31, 2004, reflecting routine fluctuations in these overnight accounts.

Total stockholder’s equity increased $210,000, or 0.3%, to $62.5 million at March 31, 2005 from $62.3 million at December 31, 2004. The increase reflected net income of $1.4 million for the three months ended March 31, 2005 partially offset by an increase in the accumulated other comprehensive loss of $1.2 million caused by an increase in intermediate-term interest rates in the debt securities markets.

Comparison of Operating Results for the Three Months Ended March 31, 2005 and 2004

Net Income. Net income increased $105,000, or 8.3%, to $1.4 million for the three months ended March 31, 2005 from $1.3 million for the three months ended March 31, 2004. The increase primarily resulted from increased net interest income and noninterest income, partially offset by a higher provision for loan losses and higher noninterest expense.

Net Interest Income Before Provision for Loan Losses. Net interest income before provision for loan losses increased $382,000, or 6.3%, to $6.4 million for the three months ended March 31, 2005. The increase reflected a $38.7 million, or 5.4%, increase in the average balance of total interest earning assets to $759.2 million for the three months ended March 31, 2005, which more than offset an 8 basis point decrease in our interest rate spread to 3.03% from 3.11%.

Interest Income. Interest income increased $817,000, or 9.1%, to $9.8 million for the three months ended March 31, 2005 from $9.0 million for the prior year period. The increase resulted from a $47.9 million, or 6.7%, increase in the average balance of total interest-earning assets, as well as an 11 basis point increase in the average yield on such assets to 5.15% for the three months ended March 31, 2005 from 5.04% for the prior year period. Interest income attributable to loans increased $1.0 million, or 14.6%, to $8.1 million for the three months ended March 31, 2005 from $7.1 million for the prior year period. The increase in interest earned on loans was due to the $68.8 million, or 13.6%, increase in the average balance of loans, coupled with a 5 basis point increase in the yield earned on such loans to 5.65% from 5.60%, as the continued low market interest rate environment combined with strong demand for residential financing in our primary market area resulted in our loan originations more than offsetting loan

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prepayments. Interest earned on investment securities, including mortgage-backed securities, decreased $316,000, or 17.1%, to $1.5 million for the three months ended March 31, 2005, from $1.8 million for the prior year period. The decrease reflected the lower average balance of such securities of $33.5 million, or 17.0%.

Interest Expense. Interest expense increased $435,000, or 14.8%, to $3.4 million for the three months ended March 31, 2005 from $2.9 million for the prior year period. The increase in interest expense was due to the $28.3 million, or 4.7%, increase in the average balance of interest-bearing liabilities to $636.6 million for the three months ended March 31, 2005 from $608.2 million for the prior year period, coupled with the increase in the average cost of such liabilities to 2.12% for the three months ended March 31, 2005 from 1.93% for the prior year period. The interest paid on deposits increased by $345,000, or 15.4%, reflecting an increase in the average cost of such deposits to 1.90% from 1.71%, while the average balance of such deposits increased by $21.9 million, or 4.2%, as we continued to expand deposit balances to fund loan growth. The interest paid on savings accounts, money market and NOW accounts, and certificates of deposit all increased. Interest paid on Federal Home Loan Bank advances increased by $90,000, or 13.8%, reflecting an increase in the average balance of such advances to $85.4 million for the three months ended March 31, 2005 from $79.3 million for the prior year period, coupled with an increase in the average cost of such advances to 3.48% from 3.29%.

Provision for Loan Losses. The provision for loan losses was $275,000 for the three months ended March 31, 2005 as compared to $113,000 for the three months ended March 31, 2004. The increase in the provision was due to a higher proportion in our loan portfolio of commercial real estate loans and commercial and industrial loans, and higher adversely classified loans (up 8.0%) and higher nonperforming loans (up 376.2%) in 2005 as compared to 2004.

While non-performing loans have gradually increased from 0.21% of total loans at December 31, 2002 to 0.78% of total loans at March 31, 2005, the increase in non-performing loans during the quarter ended March 31, 2005 was primarily due to three delinquent loans, all of which are collateralized by either residential real estate, commercial real estate or non-real estate assets. We expect that the collateral for these loans as well as the implementation of our normal collection procedures will result in a resolution of these delinquencies without loss to the Company. The allowance for loan losses was $6.1 million, or 1.07% of loans outstanding on March 31, 2005.

Noninterest Income. Noninterest income increased $16,000, or 1.4%, to $1.2 million for the three months ended March 31, 2005. Fee income on depositors’ accounts increased $114,000 to $897,000 for the three months ended March 31, 2005, reflecting growth in deposits to $638.1 million at March 31, 2005. This increase was partially offset by a $110,000 decrease in gains on the sale of securities for the three months ended March 31, 2005 compared to the earlier year period.

Noninterest Expense. Noninterest expense increased 1.2% to $5.03 million for the three months ended March 31, 2005 from $4.97 million for the prior year period. The increase reflected salary and employee benefits increases as well as increased staffing, which was partially offset by higher expenses in the 2004 period related to the conversion of United Bank to a federal charter.

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Income Tax Expense. Income tax expense increased to $903,000 for the three months ended March 31, 2005 from $830,000 for the prior year. The effective tax rate was 39.8% and 39.7% for the three months ended March 31, 2005 and 2004, respectively.

FORWARD LOOKING STATEMENTS

This prospectus contains forward-looking statements, which can be identified by the use of such words as estimate, project, believe, intend, anticipate, plan, seek, expect and similar expressions. These forward-looking statements include:

These forward-looking statements are subject to significant risks, assumptions and uncertainties, including, among other things, the following important factors that could affect the actual outcome of future events:

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Because of these and other uncertainties, our actual future results may be materially different from the results indicated by these forward-looking statements. We discuss these and other uncertainties in “Risk Factors” beginning on page 20.

HOW WE INTEND TO USE THE PROCEEDS FROM THE OFFERING

Although we will not be able to determine the amount of actual net proceeds we will receive from the sale of shares of common stock until the offering is completed, we anticipate that the net proceeds will be between $47.8 million and $65.1 million, or $75.0 million if the offering is increased by 15%.

United Financial Bancorp, Inc. intends to distribute the net proceeds from the offering as follows: