ALT5 Sigma Corp

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the Securities

Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

ALT5 SIGMA CORPORATION

(Name of Registrant as Specified In Its Charter)

Payment of Filing Fee (Check the appropriate box):

ALT5 Sigma Corporation

8548 Rozita Lee Avenue, Suite 305

Las Vegas, Nevada 89113

NOTICE OF 2025 ANNUAL MEETING OF STOCKHOLDERS

Las Vegas, Nevada

February 3, 2026

Dear Stockholder:

We cordially invite you to attend the Annual Meeting of Stockholders (the “Annual Meeting”) of ALT5 Sigma Corporation, a Nevada corporation (the “Company,” “we,” “our,” or “us”), to be held 11:00 a.m., Pacific Time, on February 27, 2026. The Annual Meeting will be held in a virtual-only format via live webcast, which you can access by visitingwww.virtualshareholdermeeting.com/ALTS2025 and entering the 16-digit control number included in your proxy materials, on your proxy card or in the instructions that accompanied your proxy materials.

Please see the “Questions and Answers about These Proxy Materials and Voting” in the accompanying Proxy Statement for more details.

The Annual Meeting is being held for the following purposes:

The Board of Directors has fixed the close of business on January 30, 2026 as the “Record Date” for the 2025 Annual Meeting. Only the holders of record of our common stock, Series B Preferred Stock, Series I Convertible Preferred Stock, Series Q Convertible Preferred Stock, and/or Series S Convertible Preferred Stock as of the close of business on the Record Date are entitled to receive notice of, and to vote at, the 2025 Annual Meeting and any adjournment thereof. We have also enclosed with this notice (i) our Annual Report on Form 10-K for the fiscal year ended December 28, 2024 and (ii) a Proxy Statement.

Your vote is extremely important regardless of the number of shares you own.

Whether you own a few shares or many, and whether or not you plan to attend the Annual Meeting in person, it is important that your shares be represented and voted at the meeting. You may vote your shares on the Internet, by telephone, or by completing, signing, and promptly returning a proxy card or you may vote in person at the Annual Meeting. Voting online, by telephone, or by returning your proxy card does not deprive you of your right to attend the Annual Meeting.

By Order of the Board of Directors,

/s/ Tony Isaac

Tony Isaac, Acting Chief Executive Officer and Corporate Secretary February 3, 2026

We have elected to utilize the “full set delivery”option and are delivering paper copies to all stockholders entitled thereto of all proxy materials, as well as providing access to those proxy materials on a publicly accessible website. Our proxy materials for the Annual Meeting are being mailed to our stockholders on or about February 3, 2026. This Proxy Statement and proxy card will also be available to our stockholders atwww.proxyvote.com on that same date.

Whether or not you expect to attend the meeting electronically, please submit a proxy or voting instructions for your shares promptly using the directions in your proxy materials or on your proxy card, or, if you elected to receive printed proxy materials by mail, your proxy card, by one of the following methods: (1) over the internet by visitingwww.proxyvote.com and entering the 16-digit control number included in your proxy materials, (2) by telephone by calling the toll-free number 1-800-690-6903, or (3) by marking, dating, and signing your proxy card and returning it in the accompanying postage-paid envelope. Even if you have voted by proxy, you may still vote if you attend the meeting electronically. Please note, however, that if your shares are held of record by a broker, bank, or other nominee and you wish to vote at the meeting, you must obtain a proxy issued in your name from that record holder.

TABLE OF CONTENTS

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ALT5 SIGMA CORPORATION

8548 Rozita Lee Avenue, Suite 305

Las Vegas, Nevada 89113

PROXY STATEMENT

FOR

ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD AT 11:00 A.M., PACIFIC TIME, ON FEBRUARY 27, 2026

INTRODUCTION

This Proxy Statement relates to the 2025 Annual Meeting of Stockholders (the “Annual Meeting”) of ALT5 Sigma Corporation (“ALT5”, the “Company”, “our”, “us”, or “we”). The Annual Meeting will be held on Friday, February 27, 2026, at 11:00 a.m., Pacific Time, at our corporate offices located at 8548 Rozita Lee Avenue, Suite 305, Las Vegas, Nevada 89113, or at such other time and place to which the Annual Meeting may be adjourned or postponed. The enclosed proxy is solicited by the Company’s Board of Directors (our “Board”). The proxy materials relating to the Annual Meeting are first being mailed to stockholders entitled to vote at the Annual Meeting on or about February 3, 2026. References in this Proxy Statement to “2024” or “fiscal 2024” refer to the Company’s fiscal year ended December 28, 2024.

The information provided under “Questions and Answers About These Proxy Materials and Voting” below is for your convenience only. You should read this entire Proxy Statement carefully. Information contained on, or that can be accessed through, our website is not intended to be incorporated by reference into this Proxy Statement and references to our website address in this Proxy Statement are inactive textual references only.

Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to be Held on February 27, 2026

We anticipate that this Proxy Statement, the Notice of Annual Meeting of Stockholders, and the form of proxy card will be mailed to our stockholders commencing on or about February 3, 2026.

We are using the “Full Set Delivery” method of providing proxy materials to stockholders. Because we have elected to utilize the “Full Set Delivery” option, we are delivering to all stockholders of record paper copies of this Proxy Statement and form of proxy card, as well as providing access to those proxy materials on a publicly accessible website. This Proxy Statement, form of proxy card, and the other Annual Meeting materials are available on the internet atwww.proxyvote.com.

Additionally, you can find a copy of this Proxy Statement and form of proxy card on the website of the Securities and Exchange Commission (the “SEC”) atwww.sec.gov, or in the “All SEC Filings” section of the “Investor Relations” section of our website athttps://ir.alt5sigma.com/all-sec-filings. You may also obtain an additional printed copy of this Proxy Statement, free of charge, from us by sending a written request to: Corporate Secretary, ALT5 Sigma Corporation, 8548 Rozita Lee Avenue, Suite 305, Las Vegas, Nevada 89113.