Up to $150,000,000Common Stock Kayne Anderson BDC, Inc. (the “Company”, “we”, “us” and “our”) is a business development company(“BDC”) that invests primarily in first lien senior secured loans with a secondary focus on unitranche and split-lien loans to private middle market companies. We are managed by our investment adviser, KA Credit Advisors,LLC (the “Advisor”), an indirect controlled subsidiary of Kayne Anderson Capital Advisors, L.P. (“KayneAnderson”), a prominent alternative investment management firm. Our investment objective is to generatecurrent income and, to a lesser extent, capital appreciation. We have entered into separate equity distribution agreements, dated March 31, 2026 (the “equitydistribution agreements”) with each of Truist Securities, Inc., RBC Capital Markets, LLC, Keefe, Bruyette&Woods, Inc., Regions Securities LLC and UBS Securities LLC (each, a “sales agent”) relating to the offer andsale of our shares of common stock, par value $0.001 (the “common shares”), pursuant to this prospectussupplement and the accompanying prospectus. In accordance with the terms of the equity distributionagreements, we may from time to time offer and sell our common stock having an aggregate offering price of upto $150 million through the sales agents. All of the common stock offered by this prospectus supplement is being sold by us. Our common stock istraded on the NewYork Stock Exchange (the “NYSE”) under the symbol “KBDC.” On March 25, 2026, the lastreported closing price of our common stock on the NYSE was $13.95 per share. The net asset value per share ofour common stock at December31, 2025 (the last date prior to the date of this prospectus for which we reportednet asset value) was$16.32 per share. The offering price per share of our common stock sold in this offeringless the sales agent commissions or discounts payable by us will not be less than the NAV per share of ourcommon stock at the time we sell common stock pursuant to this offering. Sales of our common stock, if any, under this prospectus supplement and the accompanying prospectusmay be made in transactions that are deemed to be an “at the market” offering as defined in Rule415(a)(4)under the Securities Actof1933, as amended (the “Securities Act”), including, without limitation, salesmade directly on or through the NYSE, sales made to or through market makers and sales made through anyother existing trading market or electronic communications network, and by any other method permitted by law,including, but not limited to, privately negotiated transactions, which may include block trades, as we and thesales agents may agree. None of the sales agents are required to sell any specific number or dollar amount of ourcommon shares but, if and when instructed by us, will make all sales using commercially reasonable effortsconsistent with their normal trading and sales practices on mutually agreed terms between the sales agents andus. The sales agents will be entitled to aggregate compensation of up to 1.50% of the gross sales price for anycommon stock sold, as further described herein under the caption “Plan of Distribution.” In connection with thesale of common stock on our behalf, each sales agent may be deemed to be an “underwriter” within the meaningof the Securities Act, and the compensation of each sales agent may be deemed to be underwriting commissionsor discounts. Investing in our common stock involves a high degree of risk and is highly speculative. Beforeinvesting in our common stock, you should read the discussion of the material risks of investing in oursecurities in “Risk Factors” beginning on page S-8 of this prospectus supplement, page 12 of theaccompanying prospectus and in our most recently filed Annual Report on Form10-K, as well as insubsequent filings with the SEC, which are incorporated by reference into this prospectus supplementand the accompanying prospectus. Table of Contents This prospectus supplement and the accompanying prospectus, including the information incorporated byreference, contain important information you should know before investing in our common stock. You shouldcarefully read this prospectus supplement, the accompanying prospectus, and any information incorporated byreference into each, before investing in our common stock and keep them for future reference. We file annual,quarterly and current reports, proxy statements and other information about us with the Securities and ExchangeCommission (the “SEC”). This information is available free of charge by contacting us at 717TexasAvenue,Suite 2200, Houston, Texas 77002, calling us at (713)493-2020 or visiting our corporate website located atwww.kaynebdc.com. The SEC also maintains a website at www.sec.gov that contains this information.Information on our website and the SEC’s website is not incorporated into or a part of this prospectussupplement or the accompanying prospectus. Neither the SEC nor any state securities commission has approved or