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