Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We have issued our report dated February 28, 2019, with respect to the consolidated financial statements included in the Annual Report of FTS International, Inc. on Form 10-K for the year ended December 31, 2018. We consent to the incorporation by reference of said report in the Registration Statement of FTS International, Inc. on Form S-8 (File No. 333-222892).

/s/ GRANT THORNTON LLP

Dallas, Texas

February 28, 2019