PROXY STATEMENT FOR THE SPECIAL MEETING OF STAFFING 360 SOLUTIONS, INC.AND PROSPECTUS FOR 2,108,188 SHARES OF COMMON STOCK OF ATLANTICINTERNATIONAL CORP. ATLANTIC INTERNATIONAL CORP. STAFFING 360 SOLUTIONS, INC. MERGER PROPOSAL — YOUR VOTE IS VERY IMPORTANT Dear Stockholders: On November 1, 2024, Atlantic International Corp., a Delaware corporation (“Atlantic International”), Staffing360 Solutions, Inc., a Delaware corporation (“Staffing 360”), and A36 Merger Sub, Inc., a Delawarecorporation and a wholly-owned subsidiary of Atlantic (the “Merger Sub”), entered into an Agreement andPlan of Merger (as amended by the First Amendment thereto, dated as of January 7, 2025, and as it may befurther amended from time to time, the “Merger Agreement”), for the acquisition of Staffing 360 by AtlanticInternational. Pursuant to the terms of the Merger Agreement, Atlantic International will cause Merger Sub tomerge with and into Staffing 360 (the “Merger”), with Staffing 360 surviving the Merger as a wholly-ownedsubsidiary of Atlantic International. Upon completion of the Merger, each (i) share of the outstanding commonstock of Staffing 360 (“Staffing 360 common stock”), (ii) share of the outstanding Series H preferred stock ofStaffing 360 (“Series H Preferred Stock”) and (iii) share of the outstanding Series I preferred stock of Staffing360 (“Series I Preferred Stock”) immediately prior to the Effective Time (as defined in the Merger Agreement),other than Excluded Shares (as defined in the Merger Agreement), will be canceled and converted into the rightto receive such number of shares of Atlantic International common stock equal to the number of such shares ofStaffing 360 they hold multiplied by the exchange ratio of (i) 1.202, in the case of Staffing 360 common stock,(ii) 0.25, in the case of Series H Preferred Stock, and (iii) 1.00, in the case of Series I Preferred Stock (the“Exchange Ratio”). The boards of directors of each of Atlantic International and Staffing 360 have approvedthe Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger. Immediately upon completion of the merger and the transactions contemplated in the Merger Agreement(i) Staffing 360 common stockholders, holders of preferred stock (including Staffing 360 Series H ConvertiblePreferred Stock, and preferred stock to be issued to Jackson Investment Group, and holders of certainoutstanding options and warrants to purchase shares of Staffing 360 will own approximately 17.8% of the fullydilutedequity of Atlantic International and(ii) Atlantic International stockholders,holders of certainoutstanding options and warrants to purchase shares of Atlantic International common stock will own thebalance of the fully diluted equity of the Atlantic International. Atlantic International common stock is traded on the Nasdaq Global Market under the symbol “ATLN” andStaffing 360 common stock is traded on the Nasdaq Capital Market under the symbol “STAF.” Staffing 360 will hold a special meeting of its stockholders in connection with the proposed Merger, (the“Staffing 360 special meeting” or the “special meeting”). At the Special Meeting, Staffing 360 stockholders will be asked to consider and vote on the followingproposals: (1)to adopt that Merger Agreement and the transactions contemplated therein and in connectiontherewith (the “Merger Agreement Adoption Proposal”); and (2)to approve the adjournment of the special meeting to a later date or dates, if necessary orappropriate, to solicit additional proxies if there are not sufficient votes at the time of the specialmeeting to approve the Merger Agreement Adoption Proposal (the “Adjournment Proposal”).Theboard of directors of Staffing 360 recommends that Staffing 360 stockholders vote “FOR”each of the proposals to be considered at the Special Meeting. Table of Contents The special meeting will be held on February 3, 2025, beginning at 10:00 a.m., Eastern Time, and will be“virtual,”meaningthatyoucanparticipateinthemeetingonlinebyvisitingwww.virtualshareholdermeeting.com/STAF2025SMat the appointed time and date and entering the controlnumber included in your proxy card or voting instruction form. Staffing 360 stockholders are encouraged toaccess the special meeting website before the start time. Please allow ample time for online check-in. Staffing360 stockholders will not be able to attend the special meeting in person. Completion of the Merger is conditioned upon satisfaction or waiver of all closing conditions under the MergerAgreement, including, among other things, the approval by Staffing 360 stockholders of the Staffing 360Merger Agreement adoption proposal.Your vote is very important, regardless of the number of shares youown. Whether or not you plan to attend the Special Meeting virtually, please promptly mark, sign anddate the accompanying proxy card and return it in the enclosed postage-paid envelope or authorize theindividuals named on your proxy card to v