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EXHIBIT 99.1

MKS Instruments Reports Q2 2015 Financial Results

Andover, Mass., July 22, 2015 — MKS Instruments, Inc. (NASDAQ: MKSI), a global provider of technologies that enable advanced processes and improve productivity; today reports second quarter 2015 financial results.

Second Quarter Financial Results

Sales were $218 million, an increase of 2% from $214 million in the first quarter of 2015, and an increase of 18% from $185 million in the second quarter of 2014.

Second quarter net income was $33.2 million, or $0.62 per diluted share, compared to net income of $33.8 million, or $0.63 per diluted share in the first quarter of 2015, and $21.2 million, or $0.40 per diluted share in the second quarter of 2014.

Non-GAAP net earnings, which exclude special charges and credits, were $33.1 million, or $0.62 per diluted share, compared to $35.5 million, or $0.66 per diluted share in the first quarter of 2015, and $22.6 million, or $0.42 per diluted share in the second quarter of 2014.

In the second quarter, the board of directors authorized a 3% increase in the quarterly cash dividend, to $0.17 per share, and paid a dividend of $9.1 million on June 12^th. The Company has increased its quarterly cash dividend by 13% since its inception in 2011. In addition, during the quarter, the Company repurchased 116,000 shares for $4.3 million for an average price of $37.55 per share.

Gerald Colella, Chief Executive Officer and President, said, “The second quarter was another strong quarter financially for MKS. The favorable results were driven by a continued strong environment for our semiconductor business, which achieved another record high of $154 million, while sales to all other markets again grew sequentially for the seventh straight quarter. We also announced another increase in our quarterly cash dividend and repurchased shares as part of our ongoing share buyback program.

“Reports from the recent SEMICON trade show indicate a continued healthy market for semiconductor production equipment to support the technology inflections underway. Our near-term visibility indicates a continued positive business environment in both our semiconductor and other advanced markets for the third quarter.

“Based on these factors, and looking at current business levels, we anticipate that sales in the third quarter may range from $195 million to $215 million, and at these volumes, our non-GAAP net earnings could range from $0.50 to $0.64 per share and our GAAP net income could range from $0.48 to $0.61 per share.”

Conference Call Details

A conference call with management will be held on Thursday, July 23, 2015 at 8:30 a.m. (EDT). To participate in the conference call, please dial (877) 212-6076 for domestic callers and (707) 287-9331 for international callers, and an operator will connect you. Participants will need to provide the operator with the Conference ID of 68290658, which has been reserved for this call. A live and archived webcast of the call will be available on the company’s website at www.mksinst.com.

Use of Non-GAAP Financial Results

Non-GAAP amounts exclude amortization of acquired intangible assets, costs associated with completed acquisitions, income related to the sale of excess and obsolete inventory previously written down to net realizable value, restructuring charges, discrete tax benefits and charges, and the related tax effect of these adjustments. These non-GAAP measures are not in accordance with Accounting Principles Generally Accepted in the United States of America (GAAP). MKS’ management believes the presentation of these non-GAAP financial measures is useful to investors for comparing prior periods and analyzing ongoing business trends and operating results.

About MKS Instruments

MKS Instruments, Inc. is a global provider of instruments, subsystems and process control solutions that measure, control, power, monitor and analyze critical parameters of advanced manufacturing processes to improve process performance and productivity. Our products are derived from our core competencies in pressure measurement and control, materials delivery, gas composition analysis, control and information technology, power and reactive gas generation, and vacuum technology. Our primary served markets are manufacturers of capital equipment for semiconductor devices, and for other thin film applications including flat panel displays, solar cells, light emitting diodes, data storage media, and other advanced coatings. We also leverage our technology in other markets with advanced manufacturing applications including medical equipment, pharmaceutical manufacturing, energy generation and environmental monitoring.

Forward-Looking Statements

This release contains projections or other forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, Section 27 of the Securities Act, and Section 21E of the Securities Exchange Act regarding MKS’ future growth and the future financial performance of MKS. These projections or statements are only predictions. Actual events or results may differ materially from those in the projections or other forward-looking statements set forth herein. Among the important factors that could cause actual events to differ materially from those in the projections or other forward-looking statements are the fluctuations in capital spending in the semiconductor industry, and other advanced manufacturing markets, fluctuations in net sales to MKS’ major customers, potential fluctuations in quarterly results, the challenges, risks and costs involved with integrating the operations of MKS and any acquired companies, dependence on new product development, rapid technological and market change, acquisition strategy, manufacturing and sourcing risks, volatility of stock price, international operations, financial risk management, and future growth subject to risks. Readers are referred to MKS’ filings with the Securities and Exchange Commission, including its most recent Annual Report on Form 10-K and Quarterly Reports on Form 10-Q for a discussion of these and other important risk factors concerning MKS and its operations. MKS is under no obligation to, and expressly disclaims any obligation to, update or alter its forward-looking statements, whether as a result of new information, future events or otherwise.

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Company Contact: Seth H. Bagshaw
Vice President, Chief Financial Officer and Treasurer
Telephone: 978.645.5578

Investor Relations Contact: Claire McAdams
Headgate Partners LLC
Telephone: 530.265.9899
Email: claire@headgatepartners.com

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MKS Instruments, Inc.
Unaudited Consolidated Statements of Operations
(In thousands, except per share data)

Note 1: We recorded $0.03 million of acquisition costs related to the Precisive LLC acquisition, which closed during the first quarter of 2015. We recorded $0.3 million of acquisition costs comprising of legal fees related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 2: Inventory step-up adjustment related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 3: We recorded restructuring costs related to the outsourcing of an international manufacturing operation.

Note 4: Cost of sales for the three months ended June 30, 2015 includes income related to the sale of excess and obsolete inventory previously written down to net realizable value.

Note 5: The Non-GAAP net earnings and Non-GAAP net earnings per share amounts exclude acquisition costs, an inventory step-up adjustment related to an acquisition, restructuring costs, income related to the sale of excess and obsolete inventory previously written down to net realizable value, amortization of intangible assets and the related tax effect of these adjustments to reflect the expected full year effective tax rate in the related quarter.

Note 6: The Non-GAAP income from operations and Non-GAAP operating margin percentages exclude acquisition costs, an inventory step-up adjustment related to an acquisition, restructuring costs, income related to the sale of excess and obsolete inventory previously written down to net realizable value and amortization of intangible assets.

Note 7: The Non-GAAP gross profit amounts and Non-GAAP gross profit percentages exclude an inventory step-up adjustment related to an acquisition and income related to the sale of excess and obsolete inventory previously written down to net realizable value.

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MKS Instruments, Inc.
Unaudited Consolidated Statements of Operations
(In thousands, except per share data)

Note 1: The six months ended June 30, 2014 includes a tax benefit related to the settlement of an audit and other discrete tax items during the first quarter of 2014.

Note 2: The six months ended June 30, 2015 includes acquisition costs related to the Precisive LLC acquisition, which closed during the first quarter of 2015. The six months ended June 30, 2014 includes acquisition costs comprised of legal fees related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 3: Inventory step-up adjustment related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 4: The six months ended June 30, 2015 includes restructuring charges related mainly to the outsourcing of an international manufacturing operation. The six month period ended June 30, 2014 includes restructuring charges primarily for severance related costs related to a reduction in work force throughout the Company.

Note 5: Cost of sales for the six months ended June 30, 2015 includes income related to the sale of excess and obsolete inventory previously written down to net realizable value.

Note 6: The Non-GAAP net earnings and Non-GAAP net earnings per share amounts exclude acquisition costs, an inventory step-up adjustment related to an acquisition, restructuring costs, amortization of intangible assets, income related to the sale of excess and obsolete inventory previously written down to net realizable value, discrete tax benefits and charges, and the related tax effect of these adjustments to reflect the expected full year effective tax rate in the related quarter.

Note 7: The Non-GAAP income from operations and Non-GAAP operating margin percentages exclude acquisition costs, an inventory step-up adjustment related to an acquisition, restructuring costs, income related to the sale of excess and obsolete inventory previously written down to net realizable value and amortization of intangible assets.

Note 8: The Non-GAAP gross profit amounts and Non-GAAP gross profit percentages exclude an inventory step-up adjustment related to an acquisition and income related to the sale of excess and obsolete inventory previously written down to net realizable value.

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MKS Instruments, Inc.
Reconciliation of GAAP Income Tax Rate to Non-GAAP Income Tax Rate
(In thousands)

Note 1: The three months ended March 31, 2015 includes acquisition costs related to the Precisive LLC acquisition, which closed during the first quarter of 2015. The three and six months ended June 30, 2014 include acquisition costs comprising of legal and filing fees related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 2: The three and six months ended June 30, 2014 includes an inventory step-up adjustment related to the acquisition of the Granville-Phillips division of Brooks Automation, which closed during the second quarter of 2014.

Note 3: The three and six months ended March 31, 2015 and the three and six month periods ended June 30, 2015 include restructuring charges related to the outsourcing of an international manufacturing operation. The six month period ended June 30, 2014 includes restructuring charges primarily for severance related costs related to a reduction in work force throughout the Company.

Note 4: The six months ended June 30, 2014 includes a tax benefit related to the settlement of an audit and other discrete items.

Note 5: Cost of sales for the three months ended June 30, 2015 includes income related to the sale of excess and obsolete inventory previously written down to net realizable value.

MKS Instruments, Inc.
Reconciliation of Q3-15 Guidance — GAAP Net Income to Non-GAAP Net Earnings
(In thousands, except per share data)

Note 1: The Non-GAAP adjustments are tax effected at the estimated Q3-15 tax rate of 29%.

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MKS Instruments, Inc.
Unaudited Consolidated Balance Sheet
(In thousands)

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