Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statements on Form S-3 (Nos. 333-224016 and 333-224017) and on Form S-8 (Nos. 333-173025, 333-173024, 333-162883, 333-162884, 333-162885, 333-162886, 333-121089, and 333-233226) of Merck & Co., Inc. of our report dated February 26, 2020 relating to the financial statements and the effectiveness of internal control over financial reporting, which appears in this Form 10-K.

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

Florham Park, New Jersey

February 26, 2020