Exhibit 23.1
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
We consent to the incorporation by reference in Registration Statement Nos.333-34450 and333-109753 on FormS-3 and Registration Statement Nos.333-78069,333-78071,333-78073,333-31224,333-54486,333-54488,333-54490,333-90498,333-90500,333-90502,333-116385,333-116387,333-116389,333-127221,333-161211,333-195750,333-211026, and333-229483 on FormS-8 of MKS Instruments, Inc. of our report dated June 8, 2018, relating to the financial statements of Electro Scientific Industries, Inc. appearing in Item 8 of the Annual Report on Form10-K of Electro Scientific Industries, Inc. for the year ended March 31, 2018, incorporated by reference in the Current Report on Amended Form8-K of MKS Instruments, Inc. filed on April 15, 2019.
/s/ Deloitte & Touche LLP
Portland, Oregon
April 15, 2019