MKS Instruments (MKSI) 10-K 2017 FY Annual report

EXHIBIT 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement on FormS-3(Nos.333-34450 and333-109753) andS-8(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, and333-211026) of MKS Instruments, Inc. of our reportdated February 28, 2018 relating to the consolidated financial statements, financial statement schedule, and the effectiveness of internal control over financial reporting, which appears in this Form10-K.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

February 28, 2018