Sec Form 4 Filing - Apollo Principal Holdings B, L.P. @ Apollo S3 Private Markets Fund - 2025-10-29

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person Apollo Principal Holdings B, L.P. 2. Issuer Name and Ticker or Trading Symbol Apollo S3 Private Markets Fund [ NONE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 9 W. 57TH STREET, 41ST FLOOR, 3. Date of Earliest Transaction (MM/DD/YY) 10/29/2025 (Street) NEW YORK, NY10019 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class I Shares of Beneficial Ownership 10/29/2025 J( 1 ) 23,543 D $ 0 ( 1 ) 1,200,937 I See Footnote ( 2 ) ( 4 ) Class I Shares of Beneficial Ownership 10/29/2025 J( 5 ) 5,050 A $ 0 2,025,011 I See Footnotes ( 3 ) ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Apollo Principal Holdings B, L.P. 9 W. 57TH STREET, 41ST FLOOR NEW YORK, NY10019 X Apollo Principal Holdings B GP, LLC 9 W. 57TH STREET, 41ST FLOOR NEW YORK, NY10019 X APO Corp. 100 WEST PUTNAM AVENUE GREENWICH, CT06830 X Apollo S3 Holdings (ASPM AIV), L.P. 9 W. 57TH STREET, 42ND FLOOR NEW YORK, NY10019 X Apollo S3 Advisors, L.P. 190 ELGIN AVENUE GEORGE TOWN, GRAND CAYMAN, E9KYI-9808 X Sliders Advisors GP, LLC 9 W. 57TH STREET, 42ND FLOOR NEW YORK, NY10019 X APH Holdings (DC), L.P. C/O WALKERS CORPORATE LIMITED 190 ELGIN AVENUE GEORGE TOWN, GRAND CAYMAN, E9KYI-9898 X Signatures Apollo Principal Holdings B, L.P., By: Apollo Principal Holdings B GP, LLC, its general partner, Name: William B. Kuesel, Title: Vice President, /s/ William B. Kuesel 10/31/2025 Signature of Reporting Person Date Apollo Principal Holdings B GP, LLC, Name: William B. Kuesel, Title: Vice President, /s/ William B. Kuesel 10/31/2025 Signature of Reporting Person Date APO Corp., Name: William B. Kuesel, Title: Vice President, /s/ William B. Kuesel 10/31/2025 Signature of Reporting Person Date Apollo S3 Holdings (ASPM AIV), L.P., By: Apollo S3 Advisors, L.P., its general partner, By: Sliders Advisors GP, LLC, its general partner, By: /s/ James Elworth, Name: James Elworth, Title: Vice President 10/31/2025 Signature of Reporting Person Date APH Holdings (DC), L.P., By: Apollo Principal Holdings B GP, LLC, its general partner, By: /s/ Kristin Hester, Name: Kristin Hester, Title: Vice President 10/31/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Apollo S3 RIC Management, L.P. (the "Adviser") and/or its affiliates may purchase shares on behalf of investors (or deliver to such investors shares from the assets of the Adviser or its affiliates) that contributed capital to Apollo S3 Private Markets Fund (the "Fund") by June 30, 2025, up to 3% of such investors' shares. This transaction reflects a transfer by Apollo Principal Holdings B, L.P., an affiliate of the Adviser, to the eligible investors described above for no consideration. ( 2 )These securities are held directly by Apollo Principal Holdings B, L.P. ( 3 )These securities are held directly by Apollo S3 Holdings (ASPM AIV), L.P., which received shares as part of the transaction noted in footnote (1) above. Apollo S3 Advisors, L.P. is the general partner of Apollo S3 Holdings (ASPM AIV), L.P. The general partner of Apollo S3 Advisors, L.P. is Sliders Advisors GP, LLC. The sole member of Sliders Advisors GP, LLC is APH Holdings (DC), L.P. ( 4 )Apollo Principal Holdings B GP, LLC is the general partner of each of Apollo Principal Holdings B, L.P. and APH Holdings (DC), L.P. The sole member of Apollo Principal Holdings B GP, LLC is APO Corp. Each of Apollo S3 Advisors, L.P., Sliders Advisors GP, LLC, APH Holdings (DC), L.P., Apollo Principal Holdings B, L.P., Apollo Principal Holdings B GP, LLC and APO Corp. disclaims beneficial ownership of these securities, except to the extent of their pecuniary interest therein, if any, and the filing of this report shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities for purposes of Section 13(d) or 13(g) of the Securities Exchange Act of 1934, as amended, or for any other purpose. ( 5 )Reflects shares acquired in the transaction noted in footnote (1) above.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.