Exhibit 23.1
Consent of Independent Registered Public Accounting Firm
We consent to the reference to our firm under the caption "Experts" in this Registration Statement (Form S-3) and related Prospectus of Mersana Therapeutics, Inc. for the registration of shares of common stock, preferred stock, warrants and units and to the incorporation by reference therein of our reports dated February 26, 2021, with respect to the consolidated financial statements of Mersana Therapeutics, Inc., and the effectiveness of internal control over financial reporting of Mersana Therapeutics, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2020, filed with the Securities and Exchange Commission.
| /s/ Ernst & Young LLP | |
| Boston, Massachusetts | |
| November 9, 2021 | |
