EXHIBIT 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-3 of our report dated February 27, 2018, relating to the consolidated financial statements of Sierra Oncology, Inc. and subsidiaries (the “Company”) appearing in the Annual Report on Form 10-K of the Company for the year ended December 31, 2017, and to the reference to us under the heading “Experts” in the Prospectus, which is part of this Registration Statement.

/s/ Deloitte & Touche LLP

Grand Rapids, MI

June 15, 2018