Prospectus by Investment Company (Form 497)

LORD ABBETT SERIES FUND, INC.

Bond Debenture Portfolio

Supplement dated November 4, 2026 to the

Summary Prospectus, Prospectus and Statement of Additional Information, each
dated May 1, 2026, as supplemented

The following table replaces the table in the subsection under "Management-Portfolio Managers" on page 10 of the summary prospectus and on page 11 of the statutory prospectus:

The following paragraph replaces the fifth paragraph under "Management and Organization of the Funds" beginning on page 35 of the statutory prospectus:

Steven F. Rocco, Partner and Co-Head of Taxable Fixed Income, heads the Fund's team. Mr. Rocco joined Lord Abbett in 2004. Additional members of the Fund's team are Robert A. Lee, Partner and Co-Head of Taxable Fixed Income, Andrew H. O'Brien, Partner and Portfolio Manager, Robert S. Clark, Portfolio Manager, and Christopher J. Gizzo, Partner and Deputy Director of Leveraged Credit. Messrs. Lee, O'Brien, Clark, and Gizzo joined Lord Abbett in 1997, 1998, 2010, and 2008, respectively. Messrs. Rocco, Lee, O'Brien, Clark, and Gizzo are jointly and primarily responsible for the day-to-day management of the Fund.

The following rows replace the applicable rows of the corresponding table under the heading "Bond Debenture Portfolio" in the subsection titled "Portfolio Manager Information-Other Accounts Managed" on page 7-2 of the statement of additional information:

¹Included in the number of other accounts and total assets are two accounts with respect to which the management fee is based on the performance of the account; such accounts total approximately $1,447.1 million in assets.

Capitalized terms used in this Supplement shall, unless otherwise defined herein, have the same meaning as given in the Prospectuses and/or SAIs.

Please retain this document for your future reference.