Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the captions “Experts” in the Registration Statement (Form S-3 No. 333-                ) and related Prospectus of MRC Global Inc. for the registration of shares of its common stock and to the incorporation by reference therein of our reports dated February 22, 2013, with respect to the consolidated financial statements and the effectiveness of internal control over financial reporting of MRC Global Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2012, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP                

Charleston, West Virginia

March 4, 2013