Exhibit 5.1

300 COLORADO STREET SUITE 1800 AUSTIN, TX 78701   TELEPHONE: 512.617.0650 FACSIMILE: 737.910.0730   WWW.MOFO.COM MORRISON & FOERSTER LLP   AUSTIN, BEIJING, BERLIN, BOSTON, BRUSSELS, DENVER, HONG KONG, LONDON, LOS ANGELES, MIAMI, NEW YORK, PALO ALTO, SAN DIEGO, SAN FRANCISCO, SHANGHAI, SINGAPORE, TOKYO, WASHINGTON, D.C.

April 19, 2024

Centuri Holdings, Inc.

19820 North 7^th Avenue, Suite 120

Phoenix, AZ 85027

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

We are acting as counsel to Centuri Holdings, Inc., a Delaware corporation (the “Company”), in connection with its registration statement on Form S-8 (the “Registration Statement”), filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Securities Act”), relating to the proposed offering of up to 6,932,602 shares (the “Shares”) of the Company’s common stock, $0.01 par value per share, all of which Shares may be issued pursuant to awards under the Company’s Omnibus Incentive Plan (the “Plan”).

As counsel for the Company, we have examined originals or copies, certified or otherwise identified to our satisfaction, of such documents, corporate records, certificates of public officials and other instruments as we have deemed necessary for the purposes of rendering this opinion, and we are familiar with the proceedings taken and proposed to be taken by the Company in connection with the authorization, issuance and sale of the Shares. In our examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals and the conformity with the originals of all documents submitted to us as copies. This opinion letter is given, and all statements herein are made, in the context of the foregoing.

This opinion letter is based as to matters of law solely on the General Corporation Law of the State of Delaware as currently in effect. We express no opinion herein as to any other laws, statutes, ordinances, rules, or regulations.

Based upon, subject to and limited by the foregoing, we are of the opinion that following (i) effectiveness of the Registration Statement, (ii) issuance of the Shares pursuant to the terms of the Plan, and (iii) receipt by the Company of the consideration for the Shares specified in the applicable resolutions of the Board of Directors of the Company or a duly authorized committee thereof and the Plan, the Shares will be validly issued, fully paid and nonassessable.

Centuri Holdings, Inc.

April 19, 2024

Page Two

This opinion letter has been prepared for use in connection with the Registration Statement. We assume no obligation to advise you of any changes in the foregoing subsequent to the effective date of the Registration Statement.

We consent to the use of this opinion as an exhibit to the Registration Statement, and we consent to the reference of our name wherever appearing in the Registration Statement and any amendments thereto. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act.

Very truly yours,

/s/ Morrison & Foerster LLP

Morrison & Foerster LLP