Company: MTZ
Filing Date: 2025-02-28
Form Type: S-3ASR
Source: 0001193125-25-042499
Chunk: 1

Company: MASTEC INC
Filing Date: 2025-02-28
Form: S-3ASR
Chunk 1
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 shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☒ If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-acceleratedfiler, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2of the Exchange Act.

| Large accelerated filer |     | ☒ |     | Accelerated filer         |     | ☐ |
| Non-accelerated filer   |     | ☐ |     | Smaller reporting company |     | ☐ |
|                         |     |   |     | Emerging growth company   |     | ☐ |

If an emerging growth company, indicate by checkmark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

We are filing this registration statement solely to replace MasTec, Inc.’s registration statement on Form S-3
(File No. 333-268812), filed with the Securities and Exchange Commission on December 15, 2022 (the “Expiring Registration Statement”), that is scheduled to expire on December 14, 2025
pursuant to Rule 415(a)(5) under the Securities Act of 1933, as amended. In accordance with Rule 415(a)(6), effectiveness of this registration statement will be deemed to terminate the Expiring Registration Statement.

PROSPECTUS

Common Stock, Preferred Stock,

Depositary Shares, Debt Securities, Warrants,

Stock Purchase Contracts and Stock Purchase Units

We are MasTec, Inc., a
corporation incorporated under the laws of the State of Florida. This prospectus relates to the public offer and sale of common stock, preferred stock, depositary shares, debt securities, warrants, stock purchase contracts and stock purchase units
that we may offer from time to time in one or more series. We and/or selling security holders may offer