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 March 26, 2018 relating to the consolidated financial statements and financial statement schedule of Athenex, Inc. and subsidiaries (the “Company”) (which report expresses an unqualified opinion and includes an explanatory paragraph regarding a going concern uncertainty) appearing in the Annual Report on Form 10-K of Athenex, Inc. 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

Williamsville, New York

September 24, 2018