EXHIBIT 99.1

MKS Instruments Reports Second Quarter 2020 Financial Results

Andover, MA, July 29, 2020 — MKS Instruments, Inc. (NASDAQ: MKSI), a global provider of technologies that enable advanced processes and improve productivity, today reported second quarter 2020 financial results.

“We are pleased with our strong financial performance, particularly given the global factory and supply chain disruptions we faced entering the quarter. This is a validation of our world class operational execution and our unique offering of critical enabling technologies. Robust year-over-year Semiconductor Market revenue growth of 50% was driven by broad-based demand across our portfolio – in particular for our Power Solutions business, where we delivered record revenue led by demand from leading-edge semiconductor applications,” said John TC Lee, President and Chief Executive Officer.

Mr. Lee added, “We are encouraged with the continued stabilization in our Advanced Markets, with strong growth in PCB drilling applications, primarily offset by lower revenue from certain industrial applications.”

“The sequential improvement in our second quarter non-GAAP operating margin is a testament to our ability to drive operating leverage in our financial model. We will continue to manage our business with a focus on sustainable and profitable growth,” said Seth H. Bagshaw, Senior Vice President and Chief Financial Officer.

Mr. Bagshaw added, “We delivered record operating and free cash flow in the second quarter, and our balance sheet remains strong, as our net leverage ratio exiting the second quarter further decreased to 0.5 times.”

Third Quarter 2020 Outlook

Based on current business levels, the Company expects revenue in the third quarter of 2020 could range from $535 million to $585 million. At these volumes, GAAP net income could range from $1.30 to $1.68 per diluted share and non-GAAP net earnings could range from $1.55 to $1.95 per diluted share.

Conference Call Details

A conference call with management will be held on Thursday, July 30, 2020 at 8:30 a.m. (Eastern Time). To access a live webcast of the conference call and related presentation materials management will refer to during the call, visit MKS’ website at www.mksinst.com and click on Company – Investor Relations – Investor Overview. The webcast and related presentation materials will be listed in the calendar of events. To participate by telephone, please dial (877) 212-6076 for domestic callers or (707) 287-9331 for international callers, provide the operator with Conference ID (1428938), and access the presentation materials on MKS’ website. Participants are asked to access the live webcast or dial in at least 15 minutes in advance to ensure a timely connection. An archive of the webcast and related presentation materials will be available on MKS’ website.

About MKS Instruments

MKS Instruments, Inc. is a global provider of instruments, systems, subsystems and process control solutions that measure, monitor, deliver, analyze, power and control critical parameters of advanced manufacturing processes to improve process performance and productivity for our customers. Our products are derived from our core competencies in pressure measurement and control, flow measurement and control, gas and vapor delivery, gas composition analysis, electronic control technology, reactive gas generation and delivery, power generation and delivery, vacuum technology, lasers, photonics, optics, precision motion control, vibration control and laser-based manufacturing systems solutions. We also provide services relating to the maintenance and repair of our products, installation services and training. Our primary served markets include semiconductor, industrial technologies, life and health sciences, research and defense. Additional information can be found at www.mksinst.com.

Use of Non-GAAP Financial Results

This press release includes measures that are not in accordance with U.S. generally accepted accounting principles (“Non-GAAP measures”). These Non-GAAP measures should be viewed in addition to, and not as a substitute for, MKS’ reported GAAP results, and may be different from Non-GAAP measures used by other companies. In addition, these Non-GAAP measures are not based on any comprehensive set of accounting rules or principles. MKS management believes the presentation of these Non-GAAP measures is useful to investors for comparing prior periods and analyzing ongoing business trends and operating results. For further information regarding these Non-GAAP measures, please refer to the tables presenting reconciliations of our Non-GAAP results to our U.S. GAAP results and the “Notes on our Non-GAAP Financial Information” at the end of this press release.

Selected GAAP and Non-GAAP Financial Measures

(In millions, except per share data)

Second Quarter 2020 Financial Results

Net revenues in the second quarter of 2020 were $544 million, an increase of 2% from $536 million in the first quarter of 2020, and an increase of 15% from $474 million in the second quarter of 2019. The increase in net revenues was driven largely by increased demand from customers in the Semiconductor Market. Net revenues in the Semiconductor Market were $321 million in the second quarter of 2020, a sequential increase of 3%. Net revenues in Advanced Markets were $223 million in each of the first and second quarters of 2020.

Net income in the second quarter of 2020 was $74 million, or $1.33 per diluted share, compared to net income of $69 million, or $1.25 per diluted share, in the first quarter of 2020, and $38 million, or $0.69 per diluted share, in the second quarter of 2019.

Net income in the second quarter of 2020 included restructuring and other costs of $3 million, acquisition and integration costs of $1 million, which were primarily related to the acquisition of Electro Scientific Industries, Inc., (“ESI”) and $1 million of net credits related to the COVID-19 pandemic.

Non-GAAP net earnings, which exclude special charges and credits, were $89 million, or $1.62 per diluted share, in the second quarter of 2020, compared to $85 million, or $1.54 per diluted share, in the first quarter of 2020, and $60 million or $1.09 per diluted share, in the second quarter of 2019.

Additional Financial Information

At June 30, 2020, the Company had $607 million in cash and short-term investments, $838 million of secured term loan principal outstanding and $100 million of incremental borrowing capacity under an asset-based line of credit, subject to certain borrowing base requirements. During the second quarter of 2020, the Company paid a cash dividend of $11 million or $0.20 per diluted share.

SAFE HARBOR FOR FORWARD-LOOKING STATEMENTS

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, Section 27A of the Securities Act and 21E of the Securities Exchange Act of 1934 regarding the future financial performance, business prospects and growth of MKS Instruments, Inc. (“MKS” or the “Company”). These statements are only predictions based on current assumptions and expectations. Any statements that are not statements of historical fact (including statements containing the words “will,” “projects,” “intends,” “believes,” “plans,” “anticipates,” “expects,” “estimates,” “forecasts,” “continues” and similar expressions) should be considered to be forward-looking statements. Actual events or results may differ materially from those in the forward-looking statements set forth herein. Among the important factors that could cause actual events to differ materially from those in the forward-looking statements are the conditions affecting the markets in which MKS operates, including the fluctuations in capital spending in the semiconductor industry and other advanced manufacturing markets, fluctuations in sales to our major customers, the impact of the COVID-19 pandemic on the global economy and financial markets, including any restrictions on MKS’ operations and the operations of MKS’ customers and suppliers resulting from public health requirements and government mandates, the terms of our term loan, competition from larger or more established companies in MKS’ markets, MKS’ ability to successfully grow our business and particularly that of ESI’s business, the challenges, risks and costs involved with integrating the operations of the companies we have acquired, potential fluctuations in quarterly results, 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 the other factors described in MKS’ most recent Annual Report on Form 10-K for the year ended December 31, 2019 and any subsequent Quarterly Reports on Form 10-Q, as filed with the SEC. MKS is under no obligation to, and expressly disclaims any obligation to, update or alter these forward-looking statements, whether as a result of new information, future events or otherwise after the date of this press release.

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Company Contact:

David Ryzhik

Vice President, Investor Relations

Telephone: (978) 557-5180

Email: david.ryzhik@mksinst.com

MKS Instruments, Inc.

Unaudited Consolidated Statements of Operations

(In millions, except per share data)

MKS Instruments, Inc.

Unaudited Consolidated Balance Sheet

(In millions)

MKS Instruments, Inc.

Unaudited Consolidated Statements of Cash Flows

(In millions)

The following supplemental Non-GAAP earnings information is presented to aid in understanding MKS’ operating results:

MKS Instruments, Inc.

Schedule Reconciling Selected Non-GAAP Financial Measures

(In millions, except per share data)

MKS Instruments, Inc.

Schedule Reconciling Selected Non-GAAP Financial Measures

(In millions)

MKS Instruments, Inc.

Reconciliation of GAAP Income Tax Rate to Non-GAAP Income Tax Rate

(In millions)

MKS Instruments, Inc.

Reconciliation of GAAP Income Tax Rate to Non-GAAP Income Tax Rate

(In millions)

MKS Instruments, Inc.

Schedule Reconciling Selected Non-GAAP Financial Measures – Q3’20 Guidance

(In millions, except per share data)

MKS Instruments, Inc.

Notes on Our Non-GAAP Financial Information

Non-GAAP financial measures adjust GAAP financial measures for the items listed below. These Non-GAAP measures should be viewed in addition to, and not as a substitute for, MKS’ reported GAAP results, and may be different from Non-GAAP measures used by other companies. In addition, these Non-GAAP measures are not based on any comprehensive set of accounting rules or principles. MKS management believes the presentation of these Non-GAAP measures is useful to investors for comparing prior periods and analyzing ongoing business trends and operating results.

Note 1: During the three and six months ended June 30, 2020, we recorded COVID-19 related costs and credits that were direct, incremental and not expected to recur. The amounts consisted of US and foreign payroll-tax credits for maintaining our workforce during the pandemic, offset by shift premiums and bonuses.

Note 2: Cost of revenues during the three and six months ended June 30, 2019 includes the amortization of the step-up of inventory to fair value as a result of the ESI acquisition.

Note 3: Acquisition and integration costs were primarily related to our acquisition of ESI which closed on February 1, 2019.

Note 4: We recorded additional interest expense related to the amortization of debt issuance costs related to our Term Loan Credit Agreement and our ABL Credit Agreement.

Note 5: Restructuring and other costs during the three and six months ended June 30, 2020 and the three months ended March 31, 2020 primarily included duplicate facility costs attributed to entering into new facility leases and costs related to the closing of a facility in Europe. Such costs for the three months ended March 31, 2020 and six months ended June 30, 2020 were offset by an insurance reimbursement related to a legal settlement. Restructuring costs recorded during the three and six months ended June 30, 2019 consisted primarily of severance costs related to an organization-wide reduction in workforce, the consolidation of service functions in Asia and the movement of certain products to low cost regions. In the six months ended June 30, 2019, we also recorded a legal settlement.

Note 6: During the six months ended June 30, 2020 and the three months ended March 31, 2020, we recorded an asset impairment charge as a result of the write-down of long-lived assets related to the pending closure of a facility.

Note 7: We recorded fees and expenses during the six months ended June 30, 2019 related to Amendment No. 5 to our Term Loan Credit Agreement.

Note 8: We recorded windfall tax benefits on the vesting of stock-based compensation.

Note 9: We recorded a write-off of a deferred tax asset related to foreign net operating losses.

Note 10: We recorded tax adjustments during the three and six months ended June 30, 2019 resulting from additional guidance provided by tax authorities with respect to the 2017 U.S. tax reforms.

Note 11: Non-GAAP net earnings and Non-GAAP net earnings per diluted share amounts exclude net credits related to the COVID-19 pandemic, amortization of the step-up of inventory to fair value, acquisition and integration costs, amortization of debt issuance costs, restructuring and other costs, amortization of intangible assets, asset impairments, fees and expenses related to repricings of, and amendments to, our secured term loan, windfall tax adjustments related to stock compensation expense, a deferred tax write-off, tax reform adjustments and the related tax effect of these adjustments to reflect the expected full year effective tax rate in the related period.

Note 12: The Non-GAAP gross profit amount and Non-GAAP gross margin exclude net costs related to the COVID-19 pandemic and amortization of the step-up of inventory to fair value.

Note 13: Non-GAAP operating expenses exclude acquisition and integration costs, restructuring and other costs, amortization of intangible assets, asset impairments, net credits related to the COVID-19 pandemic and fees and expenses related to repricings of our secured term loan.

MKS Instruments, Inc.

Notes on Our Non-GAAP Financial Information

Note 14: Non-GAAP income from operations and Non-GAAP operating margin percentages exclude net credits related to the COVID-19 pandemic, amortization of the step-up of inventory to fair value, acquisition and integration costs, restructuring and other costs, amortization of intangible assets, an asset impairment and fees and expenses related to repricings of our secured term loan.

Note 15: EBITDA excludes net interest, income taxes, depreciation and amortization of intangible assets.

Note 16: Adjusted EBITDA excludes from EBITDA, stock-based compensation, acquisition and integration costs, net credits related to the COVID-19 pandemic, amortization of the step-up of inventory to fair value, restructuring and other costs, an asset impairment and fees and expenses related to repricings and amendments of our secured term loan.

Note 17: Non-GAAP adjustments are tax effected at applicable statutory rates resulting in a difference between the GAAP and Non-GAAP tax rates. For the three months ending September 30, 2020, we forecast a GAAP tax rate of approximately 17% and a non-GAAP tax rate of approximately 18% based on forecasted non-GAAP adjustments for the three months ending September 30, 2020, which include the related tax effects of acquisition and integration costs, restructuring and other, amortization of intangible assets and deferred financing costs.