Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement on Form S-8 of our report relating to the consolidated financial statements of Collegium Pharmaceutical, Inc. and subsidiaries (the “Company”) dated March 7, 2018 appearing in the Annual Report on Form 10-K of the Company for the year ended December 31, 2017.

/s/ Deloitte & Touche LLP

Boston, Massachusetts

June 7, 2018