Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” in this Registration Statement (Form S-3) and related Prospectus of INC Research Holdings, Inc. for the registration of shares of its common stock and to the incorporation by reference therein of our report dated February 24, 2015, with respect to the consolidated financial statements of INC Research Holdings, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2014, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Raleigh, North Carolina

December 1, 2015