Exhibit 5.1

January 30, 2013

TRI Pointe Homes, Inc.

19520 Jamboree Road, Suite 200

Irvine, California 92612

Registration Statement on Form S-1

Ladies and Gentlemen:

We refer to the Registration Statement on Form S-1 (the “462(b) Registration Statement”) being filed by TRI Pointe Homes, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “SEC”) pursuant to Rule 462(b) under the Securities Act of 1933, as amended (the “Securities Act”). The 462(b) Registration Statement relates to the registration of an increase in the aggregate offering price of shares of common stock, par value $0.01 per share (the “Shares”), of the Company above the maximum aggregate offering price of the Shares reflected in the Registration Statement on Form S-1 (File No. 333-185642) (as amended, the “Initial Registration Statement”). The 462(b) Registration Statement incorporates by reference the Initial Registration Statement, which was filed in connection with (i) the offer, issuance and sale by the Company of up to 10,000,000 Shares (the “Primary Shares”) and (ii) the offer and sale by the Selling Stockholder of up to 5,742,350 Shares (the “Secondary Shares”) (including an aggregate of up to 2,053,350 Secondary Shares which may be sold by the Selling Stockholder pursuant to the exercise of the underwriters’ option to purchase additional Shares under the Underwriting Agreement (as defined below). The Shares are to be sold by the Company and the Selling Stockholder pursuant to an underwriting agreement among the Company, the Selling Stockholder and the Underwriters named therein, the form of which has been filed as Exhibit 1.1 to the Initial Registration Statement (the “Underwriting Agreement”).

This opinion letter is being delivered in accordance with the requirements of Item 16 of Form S-1 and Item 601(b)(5) of Regulation S-K, each under the Securities Act.

In rendering the opinions expressed below, we have acted as counsel for the Company and have examined and relied upon originals, or copies certified or otherwise identified to our satisfaction, of (i) the Initial Registration Statement, (ii) the 462(b) Registration Statement, (iii) the Amended and Restated Certificate of Incorporation of the Company filed with the Secretary of State of the State of Delaware, (iv) the Bylaws of the Company, (v) the preliminary prospectus contained within the Initial Registration Statement, (vi) the form of the Underwriting Agreement

Sidley Austin (NY) LLP is a Delaware limited liability partnership doing business as Sidley Austin LLP and practicing in affiliation with other Sidley Austin partnerships.

TRI Pointe Homes, Inc.

January 30, 2013

Page 2

and (vii) such other documents and records of the Company, certificates of public officials and representatives of the Company, resolutions and forms of resolutions and other documents and have examined such questions of law and have satisfied ourselves as to such matters of fact, as we have deemed necessary or appropriate as a basis for the opinions set forth herein. We have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures, the legal capacity of all natural persons and the conformity with the original documents of any copies thereof submitted to us for our examination.

Based upon the foregoing, and subject to the qualifications and limitations set forth herein, we are of the opinion that:

1. The Primary Shares, when issued and sold by the Company as contemplated in the Initial Registration Statement, and upon payment and delivery in accordance with the Underwriting Agreement, will be validly issued, fully paid and non-assessable.

2. The Secondary Shares have been validly issued and are fully paid and non-assessable.

This opinion letter is limited to the General Corporation Law of the State of Delaware. We express no opinion as to matters relating to securities or blue sky laws of any jurisdiction or any rules or regulations thereunder.

We hereby consent to the filing of this opinion letter as an exhibit to the 462(b) Registration Statement and to all references to our firm included in or made a part of the 462(b) Registration Statement. This consent is not to be construed as an admission that we are a party whose consent is required to be filed with the 462(b) Registration Statement under Section 7 of the Securities Act or the rules and regulations of the SEC promulgated thereunder.