Company: MTZ
Filing Date: 2025-02-28
Form Type: S-3ASR
Source: 0001193125-25-042499
Chunk: 2

Company: MASTEC INC
Filing Date: 2025-02-28
Form: S-3ASR
Chunk 2
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 and sell the securities separately, together or as units, in separate classes or series, in amounts, at prices and on terms to be determined at
the time of sale and set forth in a supplement to this prospectus. You should read this prospectus, the applicable prospectus supplement and other offering materials carefully before you invest.

We and/or selling security holders may offer the securities from time to time through public or private transactions, and in the case of our common stock, on
or off the New York Stock Exchange, at prevailing market prices or at privately negotiated prices. Sales may be made directly to purchasers or to or through agents, broker-dealers or underwriters. If any agents or underwriters are involved in the
sale of any of these securities, the applicable prospectus supplement will set forth the names of the agents or underwriters and any applicable fees, commissions or discounts. Our net proceeds from the sale of securities will also be set forth in
the applicable prospectus supplement.

Our common stock is listed on the New York Stock Exchange under the symbol “MTZ.”

Before buying any offered securities, you should carefully consider the Risk Factorscontained in this prospectus, beginning on page 3.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

Prospectus dated February 28, 2025

TABLE OF CONTENTS

|                                                            |     | Page |    |
| IMPORTANT INFORMATION ABOUT THIS PROSPECTUS                |     |      |  1 |
| FORWARD-LOOKING INFORMATION                                |     |      |  2 |
| RISK FACTORS                                               |     |      |  3 |
| OUR COMPANY                                                |     |      |  4 |
| USE OF PROCEEDS                                            |     |      |  6 |
| DESCRIPTION OF COMMON AND PREFERRED STOCK                  |     |      |  7 |
| DESCRIPTION OF DEPOSITARY SHARES                           |     |      | 11 |
| DESCRIPTION OF DEBT SECURITIES                             |     |      | 15 |
| DESCRIPTION OF WARRANTS                                    |     |      | 29 |
| DESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE 
 UNITS                                                      |     |      | 31 |
| SELLING SECURITY HOLDERS                                   |     |      | 32 |
| PLAN OF DISTRIBUTION                                       |     |      | 33 |
| LEGAL MATTERS