Exhibit 15.1

Consent of Independent Registered Public Accounting Firm

Mereo BioPharma Group plc 2019 Equity Incentive Plan

Mereo BioPharma Group plc 2019 Non-Employee Equity Incentive Plan

We consent to the incorporation by reference in the following Registration Statements:

(1) Registration Statement on Form S-8 (No, 333-231636) pertaining to both the Mereo BioPharma Group plc 2019 Equity Incentive Plan and the Mereo BioPharma Group plc 2019 Non-Employee Equity Incentive Plan; and

(2) Registration Statement on Form S-8 (No. 333-236498) pertaining to both the Mereo BioPharma Group plc 2019 Equity Incentive Plan and the Mereo BioPharma Group plc 2019 Non-Employee Equity Incentive Plan; and

(3) Registration Statement on Form S-8 (No. 333-252147) pertaining to i) Mereo BioPharma Group plc 2019 Equity Incentive Plan, as amended; ii) Mereo BioPharma Group plc 2019 Non-Employee Equity Incentive Plan, as amended, iii) Mereo BioPharma Group plc Share Option Scheme 2016, as amended; iv) Mereo BioPharma Group plc Deferred Bonus Share Plan 2016, as amended; v) Mereo BioPharma Group plc Long Term Incentive Plan 2016, as amended and vi) Mereo BioPharma Group Share Option Scheme 2015, as amended; and

(4) Registration Statements on Form F-3 (No. 333-249341 and No. 333-239708) of Mereo BioPharma Group plc and in the related Prospectuses;

of our report dated March 31, 2021, with respect to the consolidated financial statements of Mereo BioPharma Group plc included in this Annual Report (Form 20-F) for the year ended December 31, 2020.

/s/ Ernst & Young LLP

London, United Kingdom

March 31, 2021