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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-173311

PROSPECTUS SUPPLEMENT

(To Prospectus dated August 19, 2011)

$30,000,000

Common Stock

We have entered into an at-the-market equity offering sales agreement, or the sales agreement, with Citadel Securities LLC, or Citadel Securities, relating to the shares of our common stock, par value $0.10 per share, offered by this prospectus supplement. In accordance with the terms of the sales agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $30,000,000 from time to time through or to Citadel Securities, as sales agent and/or principal.

Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus may be made in sales deemed to be “at-the-market” equity offerings as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, or the Securities Act. Subject to the terms of the sales agreement, we agreed to issue and sell exclusively through Citadel Securities acting as sales agent or directly to Citadel Securities acting as principal from time to time, and Citadel Securities agreed to use its commercially reasonable efforts to sell for us, the shares of our common stock offered by this prospectus supplement. Sales of the shares, if any, through Citadel Securities acting as sales agent or directly to Citadel Securities acting as principal will be made by means of ordinary brokers’ transactions on the NASDAQ Capital Market, or otherwise at market prices prevailing at the time of sale or at prices related to such prevailing market prices, or at negotiated prices, or, with our prior approval, in privately negotiated transactions, or as otherwise agreed by Citadel Securities and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

We will pay Citadel Securities a commission equal to 2% of the gross sales price per share for sales under the sales agreement where Citadel Securities is acting as agent. In connection with any sale of our common stock, Citadel Securities may be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of Citadel Securities may be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to Citadel Securities with respect to certain liabilities, including liabilities under the Securities Act.

Under the terms of the sales agreement, if we sell shares of our common stock to Citadel Securities as principal, we will enter into a separate terms agreement with Citadel Securities.

Our common stock is currently traded on the NASDAQ Capital Market under the symbol “MXWL.” On February 15, 2012, the reported closing price of our common stock was $21.10 per share.

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks that we have described in this prospectus supplement under the caption “Risk Factors” starting on page S-4 of this prospectus supplement and under the caption “Risk Factors” in our most recently filed Annual Report on Form 10-K as filed with the Securities and Exchange Commission, which is incorporated herein by reference in its entirety.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

Citadel Securities

The date of this prospectus supplement is February 16, 2012

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Prospectus Supplement

Prospectus

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ABOUT THIS PROSPECTUS SUPPLEMENT

You should rely only on information contained in this prospectus supplement, the accompanying prospectus and the documents we incorporate by reference in this prospectus supplement and the accompanying prospectus. We have not, and Citadel Securities has not, authorized anyone to provide you with information that is different. If anyone provides you with different or additional information, you should not rely on it. We are not, and Citadel Securities is not, offering to sell and seeking offers to buy shares of our common stock in any jurisdiction where the offer and sale is not permitted. You should assume that the information appearing in this prospectus supplement and the accompanying prospectus, including the documents incorporated herein and therein by reference, is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates. When we or Citadel Securities deliver this prospectus supplement or the accompanying prospectus or makes a sale pursuant to this prospectus supplement, neither we nor Citadel Securities are implying that the information is current as of the date of the delivery or sale.

This prospectus supplement is a supplement to the accompanying prospectus that is also a part of this document. This prospectus supplement and the accompanying prospectus are part of a shelf registration statement that we filed with the Securities and Exchange Commission, or the SEC. Under the shelf registration process, we may offer from time to time shares of our common stock, warrants and debt securities. We have $125,000,000 remaining under our shelf registration statement as of the date of this prospectus supplement and excluding any of the shares of our common stock that may be sold in this offering. In the accompanying prospectus, we provide you with a general description of the securities we may offer from time to time under our shelf registration statement. In this prospectus supplement, we provide you with specific information about the shares of our common stock that we are selling in this offering. This prospectus supplement and the accompanying prospectus and the documents incorporated by reference herein and therein include important information about us, our common stock being offered and other information you should know before investing. This prospectus supplement also adds, updates and changes information contained in the accompanying prospectus. You should read both this prospectus supplement and the accompanying prospectus as well as the additional information described under “Where You Can Find More Information” before investing in shares of our common stock. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or in any document incorporated by reference that was filed with the SEC before the date of this prospectus supplement, on the other hand, you should rely on the information in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

Unless the context otherwise requires, the terms “we,” “us,” “our” and similar terms used in this prospectus supplement and the accompanying prospectus refer to Maxwell Technologies, Inc. and its subsidiaries.

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RISK FACTORS

Investment in our securities involves a high degree of risk. You should carefully consider the risks described below, as well as those risks described in the sections entitled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” each contained in our most recent Annual Report on Form 10-K for the year ended December 31, 2011, which has been filed with the SEC and is incorporated herein by reference in its entirety, as well as other information in this prospectus supplement and the accompanying prospectus or in any other documents incorporated herein or therein by reference. Each of the risks described in these sections and documents could adversely affect our business, financial condition, results of operations and prospects, and could result in a complete loss of your investment. This prospectus and the incorporated documents also contain forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in these forward-looking statements as a result of certain factors, including the risks mentioned above.

Risks Related to this Offering

Our stock price is and may continue to be volatile and you may not be able to resell our securities at or above the price you paid.

The market price for our common stock is volatile and may fluctuate significantly in response to a number of factors, most of which we cannot control, such as quarterly fluctuations in financial results, announcements of new technologies impacting our products, announcements by competitors or changes in securities analysts’ recommendations could cause the price of our stock to fluctuate substantially. Each of these factors, among others, could have a material adverse effect on your investment in our securities and could result in your being unable to resell the securities that you purchase at a price equal to or above the price you paid.

Our management will have broad discretion over the use of the proceeds we receive in this offering and might not apply the proceeds in ways that increase the value of your investment.

Our management will have broad discretion to use the net proceeds from any offerings under this prospectus, and you will be relying on the judgment of our management regarding the application of these proceeds. Except as described in any prospectus supplement or in any related free writing prospectus that we may authorize to be provided to you, the net proceeds received by us from our sale of the securities described in this prospectus will be added to our general funds and will be used for our general corporate purposes. Our management might not apply the net proceeds from the offering of our securities in ways that increase the value of your investment and might not be able to yield a significant return, if any, on any investment of such net proceeds. You will not have the opportunity to influence our decisions on how to use such proceeds.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement contains, and may incorporate by reference, forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, or Securities Act, and Section 21E of the Exchange Act. These forward-looking statements relate to future events or our future performance and include, but are not limited to, statements concerning our business strategy, future commercial revenues, market growth, capital requirements, new product introductions, expansion plans and the adequacy of our funding. Other statements contained in this prospectus supplement or the accompanying prospectus that are not historical facts are also forward-looking statements. We have tried, wherever possible, to identify forward-looking statements by terminology such as “may,” “will,” “could,” “should,” “expect,” “anticipate,” “intend” “plan,” “believe,” “seek,” “estimate” and other comparable terminology. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from our historical experience and our present expectations or projections.

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Factors that could cause actual results to differ from those discussed in the forward-looking statements include, but are not limited to:

We claim the protection of the safe harbor contained in the Private Securities Litigation Reform Act of 1995. We caution investors that any forward-looking statements presented in this prospectus supplement or the accompanying prospectus or the documents incorporated by reference, or those that we may make orally or in writing from time to time, are based upon management’s beliefs and assumptions and are made based on information available to us as of the time made and the actual outcome will be affected by known and unknown risks, trends, uncertainties and factors that are beyond our control or ability to predict. Although we believe that our assumptions are reasonable, they are not guarantees of future performance and some will inevitably prove to be incorrect. As a result, our actual future results can be expected to differ from our expectations, and those differences may be material. Accordingly, investors should use caution in relying on forward-looking statements, which are based on known results and trends at the time they are made, to anticipate future results or trends.

We undertake no obligation to update or revise any forward-looking statements included or incorporated by reference in this prospectus supplement or the accompanying prospectus or to update the reasons why actual results could differ from those contained in such statements, whether as a result of new information, future events or otherwise, except to the extent required by federal securities laws. Forward-looking statements may be contained in this prospectus supplement or the accompanying prospectus (and the documents incorporated by reference herein and therein) under “Risk Factors,” or may be contained in our Annual Report on Form 10-K or in our Quarterly Reports on Form 10-Q under headings such as “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Business,” or in our Current Reports on Form 8-K, among other places. Any investor in us should consider all risks and uncertainties disclosed in our filings with the SEC described below under the heading “Where You Can Find More Information,” all of which are accessible on the SEC’s website at www.sec.gov.

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USE OF PROCEEDS

The amount of proceeds from this offering will depend upon the number of shares of our common stock sold and the market price at which they were sold over the course of this offering. We currently intend to use the net proceeds from the sale of the securities for working capital and other general corporate purposes, including:

We will have significant discretion in the use of any net proceeds. Investors will be relying on the judgment of our management regarding the application of the proceeds of any sale of the securities. We may invest the net proceeds temporarily until we use them for their stated purpose.

PLAN OF DISTRIBUTION

We have entered into a sales agreement with Citadel Securities, under which we may offer and sell shares of our common stock having an aggregate offering price of up to $30,000,000 from time to time through or to Citadel Securities, as sales agent and/or principal. Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectus may be made in sales deemed to be “at-the-market” equity offerings as defined in Rule 415 promulgated under the Securities Act. Subject to the terms of the sales agreement, we agreed to issue and sell exclusively through Citadel Securities acting as sales agent or directly to Citadel Securities acting as principal from time to time, and Citadel Securities agreed to use its commercially reasonable efforts to sell for us, the shares of our common stock. Sales of the shares, if any, through Citadel Securities acting as sales agent or directly to Citadel Securities acting as principal will be made by means of ordinary brokers’ transactions on the NASDAQ Capital Market, or otherwise at market prices prevailing at the time of sale or at prices related to prevailing market prices or at negotiated prices, or, with our prior approval, in privately negotiated transactions, or as otherwise agreed by Citadel Securities and us. As sales agent, Citadel Securities will not engage in any transactions that stabilize our common stock. Under the terms of the sales agreement, if we sell shares to Citadel Securities as principal, we will enter into a separate terms agreement with Citadel Securities.

Subject to the terms and conditions of the sales agreement, Citadel Securities will use its commercially reasonable efforts to sell shares of common stock on our behalf on a daily basis or as otherwise agreed upon by us and Citadel Securities. We will designate the maximum amount of shares of common stock to be sold through Citadel Securities on a daily basis or otherwise as we and Citadel Securities agree. We may instruct Citadel Securities not to sell shares of common stock if the sales cannot be effected at or above the price designated by us in any such instruction. We or Citadel Securities may suspend the offering of shares of common stock by notifying the other.

We will pay Citadel Securities a commission equal to 2.0% of the gross sales price per share for sales under the sales agreement where Citadel Securities is acting as agent. The remaining sales proceeds, after deducting any expenses payable by us and any transaction fees imposed by any governmental or self-regulatory organization in connection with the sales, will equal our net proceeds for the sale of the shares. All of our offering expenses will be paid by us. We estimate that the expenses of the offering payable by us, excluding commissions, will be approximately $170,000. We have also agreed to reimburse Citadel Securities for certain of its expenses as set forth in the sales agreement.

Settlement for sales of common stock will occur on the third business day that is also a trading day following the date on which any sales were made in return for payment of the net proceeds to us. There is no arrangement for funds to be received in an escrow, trust or similar arrangement. We will report at least quarterly the number of shares of common stock sold through Citadel Securities under the sales agreement or any terms agreement and the net proceeds to us.

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In connection with the sale of common stock on our behalf, Citadel Securities may be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation paid to Citadel Securities may be deemed to be underwriting commissions or discounts. We have agreed to indemnify Citadel Securities against certain liabilities, including liabilities under the Securities Act, or to contribute to payments that Citadel Securities may be required to make. Citadel Securities may engage in transactions with, or perform other services for, us and our affiliates in the ordinary course of business.

Our shares are listed on the NASDAQ Capital Market under the symbol “MXWL.”

In compliance with the guidelines of the Financial Industry Regulatory Authority, Inc. (FINRA), the maximum discount or commission to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate offering price of the shares offered pursuant to this prospectus supplement.

So long as our common stock is not an “actively-traded security” as defined under Rule 101(c)(1) of Regulation M under the Exchange Act, or Regulation M, and under certain other circumstances, Citadel Securities may in its reasonable discretion, by notice to us, delay the sales of common stock under the sales agreement and any terms agreement to such date as Citadel Securities determines is reasonably necessary to ensure compliance with Regulation M and any other applicable legal or regulatory requirements.

We and Citadel Securities each have the right, by giving written notice as specified in the sales agreement, to terminate the sales agreement in each party’s sole discretion at any time.

This summary of the material provisions of the sales agreement does not purport to be a complete statement of its terms and conditions. A copy of the sales agreement is filed with the SEC and is incorporated by reference into the registration statement of which this prospectus supplement is a part. See the section entitled “Where You Can Find More Information.”

LEGAL MATTERS

Certain legal matters relating to the validity of our common stock offered by this prospectus supplement will be passed upon for us by Gunderson Dettmer Stough Villeneuve Franklin & Hachigian LLP, San Diego, California. Kirkland & Ellis LLP, New York, New York, is counsel for Citadel Securities in connection with this offering.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3, as amended, to register the securities offered by this prospectus supplement. However, this prospectus supplement does not contain all of the information contained in the registration statement and the exhibits and schedules to the registration statement. We encourage you to carefully read the registration statement and the exhibits and schedules to the registration statement. Statements in this prospectus supplement and the accompanying prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings. You should review the complete document to evaluate these statements.

We file annual, quarterly, and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public on the SEC’s website at www.sec.gov and on the investor relations page of our website at www.maxwell.com. Except for those SEC filings incorporated by reference in this prospectus supplement, none of the other information on our website is part of this prospectus supplement. You may also read and copy any document we file with the SEC at its public reference facilities at 100 F Street N.E., Washington, D.C. 20549. You can also obtain copies of the documents upon the payment of a duplicating fee to the SEC. Please call the SEC at 1-800-SEC-0330 for further information on the operation of the public reference facilities.

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INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to “incorporate by reference” the information we file with them, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying prospectus. Information contained in this prospectus supplement and the accompanying prospectus and information that we file with the SEC in the future and incorporate by reference in this prospectus supplement and the accompanying prospectus will automatically update and supersede this information. We incorporate by reference the documents listed below, and any future filings we will make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (i) after the date of the prospectus supplement and until the termination of this offering (other than current reports or portions thereof furnished under Item 2.02 or Item 7.01 of Form 8-K):

You can request a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

Maxwell Technologies, Inc.

Attn: Investor Relations

5271 Viewridge Court, Suite 100

San Diego, California 92123

(858) 503-3300

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PROSPECTUS

$125,000,000

MAXWELL TECHNOLOGIES, INC.

Common Stock

Warrants

Debt Securities

From time to time, we may sell up to an aggregate of $125,000,000 of our common stock, warrants or debt securities, either separately or in units, at prices and on terms that we will determine at the time of the offering. This prospectus provides a general description of these securities. We will specify in any accompanying prospectus supplement the terms of any offering.

Our common stock is listed on the Nasdaq National Market under the symbol “MXWL.” On August 1, 2011, the last reported sale price of our common stock was $16.64 per share. The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on the Nasdaq National Market or other securities exchange of the securities covered by the prospectus supplement.

Our principal executive offices are located at 5271 Viewridge Court, Suite 100, San Diego, California 92123, and our telephone number at that address is (858) 503-3300.

You should read this prospectus, the related prospectus supplement, any “free writing” prospectus that may be provided and any documents incorporated herein by referenced, carefully before you invest.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE “RISK FACTORS” ON PAGE 3 OF THIS PROSPECTUS.

This prospectus may not be used to offer or sell any securities unless accompanied by a prospectus supplement.

The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution.” If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable discounts or commissions and over allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this Prospectus is August 19, 2011.

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You should rely only on the information contained or incorporated by reference in this prospectus and any applicable free writing prospectus or prospectus supplement. We have not authorized anyone to provide you with information different from that contained or incorporated by reference in this prospectus and any applicable prospectus supplement. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained or incorporated by reference in this prospectus and any applicable free writing prospectus or prospectus supplement. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell and is seeking offers to buy only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information contained in this prospectus is accurate only as of the date on the front of this prospectus and that any information we have incorporated by reference or included in any free writing prospectus or prospectus supplement is accurate only as of the date given in the document incorporated by reference or the free writing prospectus or prospectus supplement, as applicable, regardless of the time of delivery of this prospectus, any applicable free writing prospectus or prospectus supplement, or any sale of our securities. Our business, financial condition, results of operations and prospects may have changed since that date.

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or SEC, using a “shelf” registration process. Under this shelf registration process, we may sell common stock, warrants or debt securities in one or more offerings up to a total dollar amount of $125,000,000. This prospectus provides you with a general description of the securities we may offer. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. Each time we sell common stock, warrants or debt securities, we will provide a prospectus supplement that will contain more specific information about the securities offered. We may also use a free writing prospectus or a prospectus supplement to add, update or change any of the information contained in this prospectus or in the documents we have incorporated by reference into this prospectus. To the extent that any statement made in a free writing prospectus or prospectus supplement conflicts with statements made in this prospectus, the statements made in the free writing prospectus or prospectus supplement will be deemed to modify or supersede those made in this prospectus. This prospectus, together with any applicable free writing prospectus or prospectus supplement and the materials we have incorporated by reference into this prospectus and any applicable free writing prospectus or prospectus supplement, includes all material information relating to this offering. Please carefully read this prospectus, all documents incorporated by reference, and any applicable free writing prospectus or prospectus supplement together with the additional information described below under “Where You Can Find More Information,” beginning on page 21, before buying any securities in this offering.

References in this prospectus to “Maxwell,” the “Company,” “we,” “us” and “our” refer to Maxwell Technologies, Inc. and its subsidiaries, on a consolidated basis, unless the context requires otherwise.

This prospectus and the information incorporated herein by reference includes trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus, any applicable free writing prospectus or prospectus supplement are the property of their respective owners.

THE COMPANY

We develop, manufacture and market energy storage and power delivery products for transportation, industrial, telecommunications and other applications and microelectronic products for space and satellite applications. Our products are designed and manufactured to perform reliably with minimal maintenance for the life of the applications into which they are integrated. We believe that this “life-of-the-application” reliability gives our products a competitive advantage and enables them to command higher profit margins than commodity products. We focus on the following lines of high-reliability products:

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We were incorporated under the name Maxwell Laboratories, Inc. in 1965. The Company made an initial public offering of common stock in 1983, and changed its name to Maxwell Technologies, Inc. in 1996. The address of our principal executive office is 5271 Viewridge Court, Suite 100, San Diego, California 92123, and our telephone number at that address is (858) 503-3300. Our web site address is www.maxwell.com. The information on, or that can be accessed through, our web site is not part of this prospectus.

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RISK FACTORS

An investment in our securities involves a high degree of risk. Prior to making a decision about investing in our securities, you should carefully consider the specific risk factors discussed in the sections entitled “Risk Factors” contained in any applicable free writing prospectus or prospectus supplement and our annual report on Form 10-K for the fiscal year ended December 31, 2010 and other filings with the SEC which are incorporated by reference in this prospectus, together with all of the other information contained in this prospectus, any applicable free writing prospectus or prospectus supplement, or incorporated by reference in this prospectus. These risks and uncertainties are not the only risks and uncertainties we face. Additional risks and uncertainties not presently known to us, or that we currently view as immaterial, may also impair our business. If any of the risks or uncertainties described in our SEC filings or any applicable free writing prospectus or prospectus supplement or any additional risks and uncertainties actually occur, our business, financial condition and results of operations could be materially and adversely affected. In that case, the trading price of our securities could decline and you might lose all or part of your investment.

Risks Related to this Offering

Our stock price is and may continue to be volatile and you may not be able to resell our securities at or above the price you paid.

The market price for our common stock is volatile and may fluctuate significantly in response to a number of factors, most of which we cannot control, such as quarterly fluctuations in financial results, announcements of new technologies impacting our products, announcements by competitors or changes in securities analysts’ recommendations could cause the price of our stock to fluctuate substantially. Each of these factors, among others, could have a material adverse effect on your investment in our securities and could result in your being unable to resell the securities that you purchase at a price equal to or above the price you paid.

Our management will have broad discretion over the use of the proceeds we receive in this offering and might not apply the proceeds in ways that increase the value of your investment.

Our management will have broad discretion to use the net proceeds from any offerings under this prospectus, and you will be relying on the judgment of our management regarding the application of these proceeds. Except as described in any prospectus supplement or in any related free writing prospectus that we may authorize to be provided to you, the net proceeds received by us from our sale of the securities described in this prospectus will be added to our general funds and will be used for our general corporate purposes. Our management might not apply the net proceeds from the offering of our securities in ways that increase the value of your investment and might not be able to yield a significant return, if any, on any investment of such net proceeds. You will not have the opportunity to influence our decisions on how to use such proceeds.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, the documents incorporated into this prospectus by reference herein and in any free writing prospectus or prospectus supplement that are not strictly historical in nature contain certain forward-looking statements (as such term is defined in Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended) and information relating to Maxwell that are based on the beliefs of the management of Maxwell as well as assumptions made by and information currently available to the management of Maxwell. Statements that are not based on historical facts, which can be identified by the use of such words as “likely,” “will,” “suggests,” “target,” “may,” “would,” “could,” “anticipate,” “believe,” “estimate,” “expect,” “intend,” “plan,” “predict,” “project,” and similar expressions and their variants, are forward-looking. Such statements reflect the judgment of Maxwell as of the date of this prospectus and they involve many risks and uncertainties, such as those referenced in section entitled “Risk Factors”. Our actual

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results may differ materially from those predicted in any forward-looking statements and we cannot guarantee future results, levels of activity, performance or achievements. Moreover, neither we nor any other person assumes responsibility for the accuracy and completeness of these forward-looking statements. We undertake no obligation to update forward-looking statements.

RATIO OF EARNINGS TO FIXED CHARGES

The following table sets forth our ratio of earnings to fixed charges for the periods indicated:

For the fiscal years ended December 31, 2006, 2007, 2008, 2009 and 2010, our earnings were insufficient to cover fixed charges by $11.5 million, $10.4 million, $11.5, $18.7 million and $3.5 million, respectively. For the purpose of this table, “earnings” consist of income (loss) from continuing operations before income taxes, extraordinary items, cumulative effect of accounting changes, equity in net losses of affiliates and fixed charges and “fixed charges” consist of interest expense and the portion of operating lease expense that represents interest.

HOW WE INTEND TO USE THE PROCEEDS

Unless we otherwise indicate in an applicable free writing prospectus or prospectus supplement, we currently intend to use the net proceeds from the sale of the securities for working capital and other general corporate purposes, including:

If a material part of the net proceeds is to be used to repay indebtedness, we will set forth the interest rate and maturity of such indebtedness in a prospectus supplement.

We may set forth additional information on the use of net proceeds from the sale of securities we offer under this prospectus in a free writing prospectus or prospectus supplement relating to the specific offering.

DILUTION

We will set forth in a prospectus supplement the following information regarding any material dilution of the equity interests of investors purchasing securities in an offering under this prospectus:

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DESCRIPTION OF COMMON STOCK

Our authorized capital stock consists of 40,000,000 shares of common stock, $0.10 par value. As of August 1, 2011, there were 27,978,177 shares of common stock outstanding.

The following summary description of our common stock is based on the provisions of our amended and restated certificate of incorporation and amended and restated bylaws and the applicable provisions of the Delaware General Corporation Law. This information is qualified entirely by reference to the applicable provisions of our amended and restated certificate of incorporation, amended and restated bylaws and the Delaware General Corporation Law. For information on how to obtain copies of our amended and restated certificate of incorporation and amended and restated bylaws, which are exhibits to the registration statement of which this prospectus is a part, see “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.”

Voting Rights

Each holder of our common stock is entitled to one vote for each share on all matters submitted to a vote of our stockholders, including the election of our directors. Under our amended and restated certificate of incorporation and bylaws, our stockholders will not have cumulative voting rights. Accordingly, the holders of a majority of our outstanding shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they should so choose. In all other matters, an action by our common stockholders requires the affirmative vote of the holders of a majority of our outstanding shares of common stock entitled to vote.

Dividends

Holders of our common stock are entitled to receive ratably any dividends our board of directors declares out of funds legally available for that purpose. Any dividends on our common stock will be non-cumulative.

Liquidation, Dissolution or Winding Up

If we liquidate, dissolve or wind up, the holders of our common stock are entitled to share ratably in all assets legally available for distribution to our stockholders after the payment of all of our debts and other liabilities.

Rights and Preferences

Our common stock has no preemptive, conversion or subscription rights. There are no redemption or sinking fund provisions applicable to our common stock.

Anti-Takeover Effects of Provisions of Delaware Law and Our Certificate of Incorporation and Bylaws

Delaware takeover statute

We are subject to Section 203 of the Delaware General Corporation Law, or DGCL, which regulates acquisitions of some Delaware corporations. In general, Section 203 prohibits, with some exceptions, a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years following the date of the transaction in which the person became an interested stockholder, unless:

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Section 203 of the DGCL generally defines a “business combination” to include any of the following:

In general, Section 203 defines an “interested stockholder” as any person who, together with the person’s affiliates and associates, owns, or within three years prior to the determination of interested stockholder status did own, 15% or more of a corporation’s voting stock.

Section 203 of the DGCL could depress our stock price and delay, discourage or prohibit transactions not approved in advance by our board of directors, such as takeover attempts that might otherwise involve the payment to our stockholders of a premium over the market price of our common stock.

Amended and restated certificate of incorporation and bylaw provisions

Some provisions in our certificate of incorporation and bylaws could make it more difficult for a third party to acquire control of Maxwell, even if such change in control would be beneficial to our stockholders. We have a staggered the election of our board of directors, which means that our directors are divided into three classes. The directors in each class are elected to serve three-year terms. Since the three-year terms of each class overlap the terms of the other classes of directors, the entire board of directors cannot be replaced in any one year. Furthermore, our certificate of incorporation contains a “fair price provision” which may require a potential acquirer to obtain the consent of our board to any business combination involving Maxwell.

The provisions of our certificate of incorporation and bylaws could delay, deter or prevent a merger, tender offer, or other business combination or change in control involving us that some, or a majority, of our stockholders might consider to be in their best interests. This includes offers or attempted takeovers that could result in our stockholders receiving a premium over the market price for their shares of our common stock.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is BNY Mellon Shareowner Services. BNY Mellon Shareowner Services’ address is 400 South Hope Street, 4^th Floor, Los Angeles, California 90071.

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DESCRIPTION OF WARRANTS

The following description, together with the additional information we include in any applicable free writing prospectus or prospectus supplement, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase common stock or debt securities and may be issued in one or more series. Warrants may be offered independently or together with common stock or debt securities offered by any prospectus supplement, and may be attached to or separate from those securities. While the terms we have summarized below will generally apply to any future warrants we may offer under this prospectus, we will describe the particular terms of any warrants that we may offer in more detail in the applicable prospectus supplement. The terms of any warrants we offer under a prospectus supplement may differ from the terms we describe below.

We will issue the warrants under a warrant agreement which we will enter into with a warrant agent to be selected by us. We have filed forms of the warrant agreements and the related warrant certificates for each type of warrant we may offer under this prospectus as exhibits to the registration statement of which this prospectus is a part. We use the term “warrant agreement” to refer to any of these warrant agreements. We use the term “warrant agent” to refer to the warrant agent under any of these warrant agreements. The warrant agent will act solely as an agent of ours in connection with the warrants and will not act as an agent for the holders or beneficial owners of the warrants.

The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement applicable to a particular series of warrants. We urge you to read any free writing prospectus, the applicable prospectus supplement related to the warrants that we sell under this prospectus, as well as the complete warrant agreements that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms relating to a series of warrants.

If warrants for the purchase of common stock are offered, the applicable prospectus supplement will describe the following terms, to the extent applicable:

If warrants for the purchase of debt securities are offered, the applicable prospectus supplement will describe the following terms, to the extent applicable:

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Warrants will be in registered form only.

If the warrants are offered attached to common stock or debt securities, the applicable prospectus supplement will also describe the date on and after which the holder of the warrants can transfer them separately from the related common stock or debt securities.

A holder of warrant certificates may exchange them for new certificates of different denominations, present them for registration of transfer and exercise them at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement. Until any warrants to purchase common stock are exercised, holders of the warrants will not have any rights of holders of the underlying common stock, including any rights to receive dividends or to exercise any voting rights, except to the extent set forth under “Warrant Adjustments” below. Until any warrants to purchase debt securities are exercised, the holder of the warrants will not have any of the rights of holders of the debt securities that can be purchased upon exercise, including any rights to receive payments of principal, premium or interest on the underlying debt securities or to enforce covenants in the applicable indenture.

Exercise of Warrants

Each holder of a warrant is entitled to purchase the number of shares of common stock or principal amount of debt securities at the exercise price described in the applicable prospectus supplement. After the close of business on the day when the right to exercise terminates (or a later date if we extend the time for exercise), unexercised warrants will become void.

A holder of warrants may exercise them by following the general procedure outlined below:

If you comply with the procedures described above, your warrants will be considered to have been exercised when the warrant agent receives payment of the exercise price, subject to the transfer books for the securities issuable upon exercise of the warrant not being closed on such date. After you have completed those procedures and subject to the foregoing, we will, as soon as practicable, issue and deliver to you the common stock or debt securities that you purchased upon exercise. If you exercise fewer than all of the warrants represented by a warrant certificate, a new warrant certificate will be issued to you for the unexercised amount of warrants. Holders of warrants will be required to pay any tax or governmental charge that may be imposed in connection with transferring the underlying securities in connection with the exercise of the warrants.

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Amendments and Supplements to the Warrant Agreements

We may amend or supplement a warrant agreement without the consent of the holders of the applicable warrants to cure ambiguities in the warrant agreement, to cure or correct a defective provision in the warrant agreement, or to provide for other matters under the warrant agreement that we and the warrant agent deem necessary or desirable, so long as, in each case, such amendments or supplements do not materially adversely affect the interests of the holders of the warrants.

Warrant Adjustments

Unless the applicable prospectus supplement states otherwise, the exercise price of, and the number of securities covered by, a common stock warrant will be adjusted proportionately if we subdivide or combine our common stock. In addition, unless the applicable prospectus supplement states otherwise, if we without receiving payment:

then the holders of common stock warrants will be entitled to receive upon exercise of the warrants, in addition to the securities otherwise receivable upon exercise of the warrants and without paying any additional consideration, the amount of stock and other securities and property such holders would have been entitled to receive had they held the common stock issuable under the warrants on the dates on which holders of those securities received or became entitled to receive such additional stock and other securities and property.

Except as stated above, the exercise price and number of securities covered by a common stock warrant and the amounts of other securities or property to be received, if any, upon exercise of those warrants, will not be adjusted or provided for if we issue those securities or any securities convertible into or exchangeable for those securities, or securities carrying the right to purchase those securities or securities convertible into or exchangeable for those securities.

Holders of common stock warrants may have additional rights under the following circumstances:

If one of the above transactions occurs and holders of our stock are entitled to receive stock, securities or other property with respect to or in exchange for their securities, the holders of the common stock warrants then outstanding will be entitled to receive upon exercise of their warrants the kind and amount of shares of stock and other securities or property that they would have received upon the applicable transaction if they had exercised their warrants immediately before the transaction.

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DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable free writing prospectus or prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future debt securities we may offer, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. If we indicate in a prospectus supplement, the terms of any debt securities we offer under that prospectus supplement may differ from the terms we describe below.

We may issue senior notes under a senior indenture which we will enter into with a trustee to be named in the senior indenture. We may issue subordinated notes under a subordinated indenture which we will enter into with a trustee to be named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement which includes this prospectus. We use the term “indentures” to refer to both the senior indenture and the subordinated indenture. The indentures will be qualified under the Trust Indenture Act of 1939, or the Trust Indenture Act. We use the term “trustee” to refer to either the senior trustee or the subordinated trustee, as applicable.

The following summaries of material provisions of senior notes, subordinated notes and the indentures are subject to, and qualified in their entirety by reference to, the provisions of the indenture applicable to a particular series of debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

We will describe in the applicable prospectus supplement the following terms relating to a series of notes:

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Conversion or Exchange Rights

We will set forth in the applicable prospectus supplement the terms on which a series of notes may be convertible into or exchangeable for common stock or other securities of ours. We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of common stock or other securities of ours that the holders of the series of notes receive would be subject to adjustment.

Consolidation, Merger or Sale

The indentures do not contain any covenant which restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the notes, as appropriate.

Events of Default Under the Indenture

The following are events of default under the indentures with respect to any series of notes that we may issue:

If an event of default with respect to notes of any series occurs and is continuing, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding notes of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, on and accrued interest, if any, on the notes due and payable immediately.

The holders of a majority in principal amount of the outstanding notes of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of notes, unless such holders have offered

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the trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding notes of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the notes of that series, provided that:

A holder of the notes of any series will only have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies, if:

These limitations do not apply to a suit instituted by a holder of notes if we default in the payment of the principal of, premium, if any, or interest on, the notes.

We will periodically file statements with the trustee regarding our compliance with specified covenants in the indentures.

Modification of Indenture; Waiver

We and the trustee may change an indenture without the consent of any holders with respect to specific matters, including:

In addition, under the indentures, the rights of holders of a series of notes may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding notes of each series that is affected. However, we and the trustee may only make the following changes with the consent of each holder of any outstanding notes affected:

Defeasance

The following provisions will be applicable to each series of debt securities unless we state in the applicable prospectus supplement or term sheet that the provisions of covenant defeasance and full defeasance will not be applicable to that series.

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Covenant Defeasance. Under current United States federal tax law, we can make the deposit described below and be released from some of the restrictive covenants in the indenture under which the particular series was issued. This is called “covenant defeasance.” In that event, you would lose the protection of those restrictive covenants but would gain the protection of having money and government securities set aside in trust to repay your debt securities. If you hold subordinated securities, you also would be released from the subordination provisions described under “Subordinated Indenture Provisions-Subordination” below. In order to achieve covenant defeasance, we must do the following:

If we accomplish covenant defeasance, you can still look to us for repayment of the debt securities if there were a shortfall in the trust deposit or the trustee is prevented from making payment. In fact, if one of the remaining Events of Default occurred (such as our bankruptcy) and the debt securities became immediately due and payable, there might be a shortfall. Depending on the event causing the default, you may not be able to obtain payment of the shortfall.

Full Defeasance. If there is a change in United States federal tax law, as described below, we can legally release ourselves from all payment and other obligations on the debt securities of a particular series (called “full defeasance”) if we put in place the following other arrangements for you to be repaid:

If we ever did accomplish full defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the unlikely event of any shortfall. Conversely, the trust deposit would most likely be protected from claims of our lenders and other

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creditors if we ever became bankrupt or insolvent. If you hold subordinated securities, you would also be released from the subordination provisions described later under “Subordinated Indenture Provisions-Subordination.”

Discharge

Each indenture provides that we can elect, under certain circumstances, to be discharged from our obligations with respect to one or more series of debt securities, except for obligations to:

In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue the notes of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue notes of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company, New York, New York, known as DTC, or another depository named by us and identified in a prospectus supplement with respect to that series. See “Legal Ownership of Securities” for a further description of the terms relating to any book-entry securities.

At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the notes of any series can exchange the notes for other notes of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the notes may present the notes for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the notes that the holder presents for transfer or exchange, we will not require any payment for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any notes. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the notes of each series.

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If we elect to redeem the notes of any series, we will not be required to:

Information Concerning the Trustee

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the trustee is under no obligation to exercise any of the powers given to it by the indentures at the request of any holder of notes unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any notes on any interest payment date to the person in whose name the notes, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest payment.

We will pay principal of and any premium and interest on the notes of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, will we make interest payments by check which we will mail to the holder. Unless we otherwise indicate in a prospectus supplement, we will designate the corporate trust office of the trustee in the city of New York as our sole paying agent for payments with respect to notes of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the notes of a particular series. We will maintain a paying agent in each place of payment for the notes of a particular series.

All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any notes which remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the security thereafter may look only to us for payment thereof.

Governing Law

The indentures and the notes will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

Subordination of Subordinated Notes

The subordinated notes will be unsecured and will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated notes which we may issue. It also does not limit us from issuing any other secured or unsecured debt.

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LEGAL OWNERSHIP OF SECURITIES

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities.

As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a book-entry security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not legal holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold

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beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depositary participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the legal holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the legal holders.

Special Considerations for Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, Depository Trust Company, known as DTC, will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

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Special Considerations for Global Securities

As an indirect holder, an investor’s rights relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a legal holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only in the form of a global security, an investor should be aware of the following:

Special Situations when a Global Security Will Be Terminated

In a few special situations described below, the global security will terminate, and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

The global security will terminate when the following special situations occur:

The applicable prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

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PLAN OF DISTRIBUTION

We may sell the securities being offered hereby in one or more of the following ways from time to time:

We will set forth in a free writing prospectus or prospectus supplement the terms of the offering of securities, including:

If we use underwriters for a sale of securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. The underwriters will be obligated to purchase all the securities of the series offered if they purchase any of the securities of that series. We may change from time to time any initial public offering price and any discounts or concessions the underwriters allow or reallow or pay to dealers. We may use underwriters with whom we have a material relationship. We will describe in a free writing prospectus or prospectus supplement naming the underwriter the nature of any such relationship.

We may designate agents who agree to use their reasonable efforts to solicit purchases for the period of their appointment or to sell securities on a continuing basis.

We may also sell securities directly to one or more purchasers without using underwriters or agents.

Underwriters, dealers and agents that participate in the distribution of the securities may be underwriters as defined in the Securities Act and any discounts or commissions they receive from us and any profit on their resale of the securities may be treated as underwriting discounts and commissions under the Securities Act. We will identify in a free writing prospectus or the applicable prospectus supplement any underwriters, dealers or agents and will describe their compensation. We may have agreements with the underwriters, dealers and agents to indemnify them against specified civil liabilities, including liabilities under the Securities Act. Underwriters, dealers and agents may engage in transactions with or perform services for us in the ordinary course of their businesses.

We will bear all costs, expenses and fees in connection with the registration of the securities as well as the expenses of all commissions and discounts, if any, attributable to the sales of securities by us.

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Unless otherwise specified in the applicable prospectus supplement or any free writing prospectus, each class or series of securities will be a new issue with no established trading market, other than our common stock, which is listed on the NASDAQ National Market. We may elect to list any other class or series of securities on any exchange, but we are not obligated to do so. It is possible that one or more underwriters may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities.

In connection with an offering, an underwriter may purchase and sell securities in the open market. These transactions may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of securities than they are required to purchase in the offering. “Covered” short sales are sales made in an amount not greater than the underwriters’ option to purchase additional securities, if any, from us in the offering. If the underwriters have an over-allotment option to purchase additional securities from us, the underwriters may close out any covered short position by either exercising their over-allotment option or purchasing securities in the open market. In determining the source of securities to close out the covered short position, the underwriters may consider, among other things, the price of securities available for purchase in the open market as compared to the price at which they may purchase securities through the over-allotment option. “Naked” short sales are any sales in excess of such option or where the underwriters do not have an over-allotment option. The underwriters must close out any naked short position by purchasing securities in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the securities in the open market after pricing that could adversely affect investors who purchase in the offering.

Accordingly, to cover these short sales positions or to otherwise stabilize or maintain the price of the securities, the underwriters may bid for or purchase securities in the open market and may impose penalty bids. If penalty bids are imposed, selling concessions allowed to syndicate members or other broker-dealers participating in the offering are reclaimed if securities previously distributed in the offering are repurchased, whether in connection with stabilization transactions or otherwise. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. The impositions of a penalty bid may also affect the price of the securities to the extent that it discourages resale of the securities. The magnitude or effect of any stabilization or other transactions is uncertain. These transactions may be effected on the NASDAQ National Market or otherwise and, if commenced, may be discontinued at any time.

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LEGAL MATTERS

The validity of the securities being offered hereby will be passed upon by Gunderson Dettmer Stough Villeneuve Franklin & Hachigian LLP, San Diego, California.

EXPERTS

McGladrey & Pullen, LLP, an independent registered public accounting firm, has audited our consolidated financial statements and schedule included in our Annual Report on Form 10-K for the year ended December 31, 2010, and the effectiveness of our internal control over financial reporting as of December 31, 2010, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on McGladrey & Pullen, LLP’s report, given on their authority as experts in accounting and auditing.

MATERIAL CHANGES

There have been no material changes in our affairs which have occurred since December 31, 2010 and which have not been described in a report on Form 10-Q or Form 8-K filed under the Exchange Act.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports and other information with the SEC under the Securities and Exchange Act of 1934. In addition, we have filed with the SEC a Registration Statement on Form S-3, of which this prospectus is a part, under the Securities Act of 1933, as amended, with respect to the securities offered hereby. This prospectus, which constitutes a part of the registration statement, does not contain all of the information set forth in the registration statement or the exhibits which are part of the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. You may read and copy any document that we file at the SEC’s public reference room located at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information regarding the public reference room. Our SEC filings are also available to you free of charge at the SEC’s web site at http://www.sec.gov, or at our website at http://www.Maxwell.com. The information on, or that can be accessed through, our web site is not part of this prospectus.

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INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to “incorporate by reference” the information we file with them, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this registration statement and prospectus the documents listed below, and any future filings we will make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (i) after the date of the initial registration statement but prior to effectiveness of the registration statement and (ii) after the date of this prospectus but prior to the termination of the offering of the securities covered by this prospectus (other than current reports or portions thereof furnished under Item 2.02 or Item 7.01 of Form 8-K):

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, a copy of any or all of the information that has been incorporated by reference in the prospectus, but not delivered with the prospectus, upon written or oral request at no cost to the requester. You should direct any requests to:

Maxwell Technologies, Inc.

Attn: Investor Relations

5271 Viewridge Court, Suite 100

San Diego, California 92123

(858) 503-3300

The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede previously filed information, including information contained in this document.

You should only rely on the information contained in this prospectus. We have not authorized any person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not making an offer to distribute or sell securities in any jurisdiction where the distribution or sale is not permitted. You should assume that the information appearing in this prospectus is accurate as of the date on the front cover of this prospectus only. Our business, financial condition, results of operations and prospects may have changed since that date.

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Table of Contents

$30,000,000

Common Stock

Prospectus Supplement

February 16, 2012

Citadel Securities