As filed with the Securities and Exchange Commission on November 15, 2013

Registration No. 333-179600

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1

TO

FORM S-8

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

SIRIUS XM HOLDINGS INC.

(Exact name of Company as specified in its charter)

1221 Avenue of the Americas, 36th Floor

New York, New York 10020

Telephone: (212) 584-5100

(Address including zip code, and telephone number, including area code, of principal executive offices)

SIRIUS XM RADIO 401(k) SAVINGS PLAN

(Full title of the plan)

Patrick L. Donnelly, Esq.

Executive Vice President, General Counsel and Secretary

Sirius XM Holdings Inc.

1221 Avenue of the Americas, 36^th Floor

New York, New York 10020

(Name and address of agent for service)

(212) 584-5100

(Telephone number, including area code, of agent for service)

With copies to:

Andrew R. Keller, Esq.

Simpson Thacher & Bartlett LLP

425 Lexington Avenue

New York, New York 10017-3954

(212) 455-2000

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

EXPLANATORY NOTE

Sirius XM Holdings Inc. (the “Company” or the “Registrant”), a Delaware corporation, files this Post-Effective Amendment to the Registration Statement on Form S-8 (this “Amendment”) as the successor registrant to its direct wholly-owned subsidiary Sirius XM Radio Inc. (“Predecessor”), a Delaware corporation, in accordance with Rule 414 under the Securities Act of 1933, as amended (the “Securities Act”). This Amendment is a result of Predecessor adopting a holding company organizational structure and pertains to the adoption by the Company of Registration Statement No. 333-179600 (the “Registration Statement”), originally covering shares of Predecessor’s common stock, par value $0.001 par value per share (the “Predecessor Common Stock”), and an indeterminate number of plan interests, issuable under the Sirius XM Radio 401(k) Savings Plan (the “Plan”).

Pursuant to the Agreement and Plan of Merger dated November 14, 2013 (the “Merger Agreement”), among the Company, Predecessor and Sirius XM Merger Sub Inc., a Delaware corporation, Predecessor reorganized into a holding company structure, effective as of November 15, 2013, whereby the Company became the holding company for Predecessor.

In accordance with the terms of the Merger Agreement, each outstanding share of Predecessor Common Stock was converted into one share of the Company’s common stock, par value $0.001 per share (the “Company Common Stock”). As a result of the Merger, each stockholder of Predecessor became a holder of Company Common Stock evidencing the same proportional interests in the Company and having the same designations, rights, powers and preferences and qualifications, limitations and restrictions as those securities that such stockholder held in Predecessor.

In accordance with Rule 414 under the Securities Act, the Company, as the successor registrant to Predecessor, hereby expressly adopts the Registration Statement as its own for all purposes of the Securities Act and the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Registration fees were paid at the time of filing the original Registration Statement.

PART II

INFORMATION REQUIRED IN REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference.

The following documents filed with the Securities and Exchange Commission (the “SEC”), pursuant to the Exchange Act, are hereby incorporated by reference and shall be deemed to be a part hereof from the date of filing of such document:

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All documents subsequently filed by the Company pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, after the date of this Amendment and prior to the filing of a post-effective amendment which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold, shall be deemed to be incorporated by reference in this Amendment and to be a part hereof from the date of filing of such documents. Any statement contained in a document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded for purposes of this Amendment to the extent that a statement contained herein or in any other subsequently filed document which also is or is deemed to be incorporated by reference herein modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Amendment.

Notwithstanding the foregoing, information furnished under Items 2.02 and 7.01 of any Current Report on Form 8-K, including the related exhibits, is not incorporated by reference in this Amendment or the related prospectus.

Item 4. Description of Securities.

Not applicable.

Item 5. Interest of Named Experts and Counsel.

Patrick L. Donnelly, Esq., whose legal opinion with respect to the securities registered hereunder is filed as Exhibit 5.1 hereto, is an officer of the Company and participates in the Plan and other benefit plans established by the Company.

Item 6. Indemnification of Directors and Officers.

Section 145 of the Delaware General Corporation Law (the “DGCL”) permits each Delaware business corporation to indemnify its directors, officers, employees and agents against liability for each such person’s acts taken in his or her capacity as a director, officer, employee or agent of the corporation if such actions were taken in good faith and in a manner which he or she reasonably believed to be in or not opposed to the best interests of the corporation, and with respect to any criminal action, if he or she had no reasonable cause to believe his or her conduct was unlawful. The Company’s Amended and Restated Certificate of Incorporation provides that the Company, to the full extent permitted by law, shall indemnify any of its past and present directors, officers, employees or any person that is or was serving at the request of the Company as a director, officer or employee of another enterprise if they were or are a party to, or are threatened to be made a party to, any threatened, pending or complete action, suit or proceeding. The indemnification provided therein includes expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement and may be paid by the Company in advance of the final disposition of such action, suit or proceeding. In addition, the Company’s Amended and Restated Certificate of Incorporation provides that the Company may, to the full extent permitted by law, indemnify any other person for any such expenses as to actions in their official capacity or actions in another capacity while holding such office.

As permitted by Section 102(b)(7) of the DGCL, the Company’s Amended and Restated Certificate of Incorporation provides that no director shall be liable to the Company for monetary damages for breach of fiduciary duty as a director, except for liability:

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The Company has obtained policies insuring the Company and its directors and officers against certain liabilities, including liabilities under the Securities Act.

Item 7. Exemption from Registration Claimed.

Not applicable.

Item 8. Exhibits.

For a list of exhibits, see the Exhibit Index in this Amendment, which is incorporated into this Item by reference.

Item 9. Undertakings.

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the SEC by the Company pursuant to Section 13 or Section 15(d) of the Exchange Act that are incorporated by reference in the registration statement or is contained in a form of prospectus that is filed pursuant to Rule 424(b) that is part of the registration statement.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Company certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Post-Effective Amendment No. 1 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of New York, State of New York, on this 15th day of November, 2013.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Post-Effective Amendment No. 1 to the Registration Statement has been signed on the dates indicated by the following persons in the capacities indicated:

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INDEX OF EXHIBITS

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