Ultragenyx Pharmaceutical (RARE) 8-K Ultragenyx Completes Tender Offer and Acquisition of Dimension Therapeutics

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement onForm S-3 (No.333-201838) and the Registration Statements onForm S-8(No. 333-194773,333-201843,333-209729,333-216110, and 333-221381) of Ultragenyx Pharmaceutical Inc. of our report dated March 9, 2017 relating to the financial statements of Dimension Therapeutics Inc., which is incorporated by reference in this Current Report onForm 8-K of Ultragenyx Pharmaceutical Inc.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

November 7, 2017