Bel Fuse Inc-A美股招股说明书(2026-05-14版)

PROSPECTUS SUPPLEMENT(To prospectus dated May 12, 2026) We are offering 1,500,000 shares of our Class B common stock. We have two classes of common shares: our Class A common stock and our Class B common stock. See “Description of CapitalStock.” Our common stock is listed on the Nasdaq Global Select Market under the symbol “BELFA” and “BELFB.” On May 12,2026, the closing sale price of our Class B common stock on the Nasdaq Global Select Market was $298.22 per share. We have granted the underwriters a 30-day option to purchase up to an additional 225,000 shares of Class B common stock from us, atthe public offering price, less the underwriting discounts and commissions. Investing in our securities involves a high degree of risk. Please read “Risk Factors” beginning on page S-3 of this prospectussupplement, page 10 and page 6in the accompanying prospectus, and under similar headings in the documents that areincorporated by reference into this prospectus supplement concerning factors you should carefully consider before investing inour securities. PerShareTotalPublic offering price$266.00$399,000,000Underwriting discounts and commissions (1)$9.975$ 14,962,500Proceeds, before expenses, to us$256.025$384,037,500 (1)See the section titled “Underwriting (Conflicts of Interest)” beginning on page S-12 for a description of the compensation payableto the underwriters. Delivery of the Class B common stock will be made on or about May 15, 2026 through the book-entry facilities of The DepositaryTrust Company. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of thesesecurities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Anyrepresentation to the contrary is a criminal offense. TABLE OF CONTENTS PROSPECTUS SUPPLEMENT PageAbout this Prospectus SupplementS-iiCautionary Statement Regarding Forward-Looking StatementsS-ivProspectus Supplement SummaryS-1Risk FactorsS-3Dividend PolicyS-5Use of ProceedsS-6Material U.S. Federal Income Tax Consequences for Investors in Common StockS-7Underwriting (Conflicts of Interest)S-12Legal MattersS-19ExpertsS-19Where You Can Find More InformationS-19Incorporation of Certain Information by ReferenceS-20 PROSPECTUS DATED MAY 12, 2026 PageAbout this Prospectus1Where You Can Find More Information1Incorporation of Certain Information by Reference2Special Note Regarding Forward-Looking Statements3About the Company5Use of Proceeds7Description of Securities We May Offer8Description of Capital Stock9Description of Warrants15Description of Debt Securities17Description of Depository Shares24Description of Units26Plan of Distribution27Legal Matters30Experts30 ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement is part of an automatic shelf registration statement on Form S-3 (File No. 333- 295813) that we filedwith the Securities and Exchange Commission (the “SEC”), on May 12, 2026 as a “well-known seasoned issuer” as defined in Rule405 of the Securities Act. This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering ofClass B common stock. The second part is the accompanying prospectus, which provides more general information, some of whichmay not apply to this offering. The information included or incorporated by reference in this prospectus supplement also adds to,updates and changes information contained or incorporated by reference in the accompanying prospectus. If information included orincorporated by reference in this prospectus supplement is inconsistent with the accompanying prospectus or the informationincorporated by reference therein, then this prospectus supplement or the information incorporated by reference in this prospectussupplement will apply and will supersede the information in the accompanying prospectus and the documents incorporated byreference therein. However, if any statement in the accompanying prospectus is inconsistent with a statement in another documentwith a later date that is incorporated by reference herein, the statement in the document having the later date modifies and supersedesthe earlier statement. Before buying any of the shares of Class B common stock offered hereby, we urge you to read carefully this prospectussupplement and the accompanying prospectus, together with the information incorporated herein by reference as described in thesection titled “Incorporation of Certain Information by Reference,” as well as the additional information described in this prospectussupplement in the section titled “Where You Can Find More Information.” We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to anydocument that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in somecases, for the purpose of allocating risk among the par