EX-5.1

Exhibit 5.1

LOGO

June 3, 2024

MasTec, Inc.

800 S. Douglas Road

12th Floor

Coral Gables, Florida 33134

Re: Registration Statement on Form S-8 for the MasTec, Inc. Amended and Restated 2011 Employee Stock Purchase Plan

Ladies and Gentlemen,

On or about the date hereof, MasTec, Inc., a Florida corporation (the “Company”), transmitted for filing with the Securities and Exchange Commission (the “Commission”) a Registration Statement on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Act”). The Registration Statement relates to the offering and sale by the Company of up to an aggregate of 1,000,000 shares (the “Shares”) of the Company’s common stock, $0.10 per share (“Common Stock”), under the MasTec, Inc. Amended and Restated 2011 Employee Stock Purchase Plan (as amended to date, the “Restated 2011 ESPP”). We have acted as counsel to the Company in connection with the preparation and filing of the Registration Statement.

In connection therewith, we have examined and relied upon the original or a copy, certified or otherwise identified to our satisfaction, of: (i) the Company’s Amended and Restated Articles of Incorporation, as amended and restated to the date hereof (the “Articles”), and Bylaws, as amended to the date hereof; (ii) records of corporate proceedings of the Company related to the Restated 2011 ESPP; (iii) the Registration Statement and exhibits thereto; and (iv) such other documents, instruments and records as we have deemed necessary for the expression of the opinions contained herein. In making the foregoing examinations, we have relied, without investigation, on each of the following assumptions: (a) the legal capacity of each natural person to take all actions required of each such person in connection with the Registration Statement and the registration, issuance and sale of the Shares, (b) the genuineness of all signatures, the completeness of all documents submitted to us, the authenticity of all documents reviewed by us as originals, the conformity to original documents of all documents reviewed by us as duplicates or certified or conformed photocopies, (c) as to matters of fact, the truthfulness, accuracy and completeness of the information, representations and warranties of the Company made in the Registration Statement and in the records, documents, instruments, certificates and statements we have reviewed, (d) the due execution and delivery of all documents (except that no such assumption is made as to the Company) where due execution and delivery are a prerequisite to the effectiveness thereof, (e) that there has been no undisclosed waiver of any right, remedy or provision contained in such documents and (f) that the total number of shares of common stock issued and outstanding after the issuance of any of the Shares will not exceed the number of shares of common stock that the Company then has the authority to issue under the Articles. As to various questions of fact material to this opinion, we have relied, to the extent we deemed reasonably appropriate, upon statements and representations of officers or directors of the Company and upon documents, records and instruments furnished to us by the Company, without independently checking or verifying the accuracy of such documents, records and instruments.

Based upon the foregoing examination, and subject to the assumptions, qualifications and limitations stated herein, and assuming that (i) the Company reserves an adequate number of authorized and unissued shares of Common Stock available for issuance pursuant to the Restated 2011 ESPP and (ii) the consideration, if any, for the Shares is actually received by the Company and the Shares are issued pursuant to the Restated 2011 ESPP in accordance with the terms of the Restated 2011 ESPP, we are of the opinion that the Shares will be duly authorized, validly issued, fully paid and nonassessable.