SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2(a)

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 9)*

Allergan, Inc.

(Name of Issuer)

COMMON STOCK, $0.01 PAR VALUE

(Title of Class of Securities)

018490102

(CUSIP Number)

Valeant Pharmaceuticals International, Inc.

Robert R. Chai-Onn

2150 St. Elzéar Blvd. West

Laval, Quebec

Canada, H7L 4A8

(514) 744-6792

With a copy to:

Alison S. Ressler

Sullivan & Cromwell LLP

1888 Century Park East

Los Angeles, California 90067-1725

(310) 712-6600

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

November 19, 2014

(Date of Event which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this Schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box   ¨.

Note. Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See § 240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

This Amendment No. 9 relates to the Schedule 13D filed on April 21, 2014, as amended prior to the date of this Amendment No. 9 (as so amended, the “Original 13D”), by Valeant Pharmaceuticals International, Inc., a corporation continued under the laws of British Columbia (“Valeant”), and Valeant Pharmaceuticals International, a Delaware corporation and a wholly owned subsidiary of Valeant (“Valeant USA” and, together with Valeant, the “Reporting Persons”), relating to common shares, par value $0.01 (the “Common Stock”), of Allergan, Inc., a Delaware corporation (the “Issuer”). Capitalized terms used but not defined herein shall have the meaning set forth in the Original 13D.

Item 4 of the Original 13D is hereby amended and supplemented by adding the following information:

On November 18, 2014, Pershing Square filed a Form RW with the Securities and Exchange Commission (the “SEC”) withdrawing its previously filed Definitive Proxy Statement and suspended all solicitation efforts with respect to the December 18 special meeting of Allergan shareholders.

On November 19, 2014, Valeant withdrew its exchange offer to acquire all of the outstanding shares of the Issuer’s Common Stock and requested the withdrawal of its Registration Statement on Form S-4 filed with the SEC on June 18, 2014, as amended on July 22, 2014, August 22, 2014 and September 22, 2014, together with all exhibits thereto. Valeant is no longer seeking a merger or other business combination with the Issuer.

On November 20, 2014, Valeant, Valeant USA, PS Fund 1 and Pershing Square entered into an agreement (the “November 20 Agreement”) amending their letter agreement dated February 25, 2014. Pershing Square informed the Reporting Persons that on November 19, 2014 and November 20, 2014, PS Fund 1 sold all of the 2,242,560 shares of Common Stock allocated to Valeant USA. As a result of the allocations required by the November 20 Agreement, Valeant USA is no longer a member of PS Fund 1 and Valeant, Valeant USA and their affiliates have no further interest in PS Fund 1, except for the right to receive payments required by the November 20 Agreement.

The November 20 Agreement is filed as Exhibit 99.1 and is incorporated by reference into this Item 4 as if restated in full herein. The foregoing description of the November 20 Agreement is qualified in its entirety by reference to the November 20 Agreement.

Item 5 of the Original Schedule 13D is hereby amended and supplemented by adding the following information:

(a), (b), (c) Pershing Square has informed the Reporting Persons that between November 19, 2014 and November 20, 2014, PS Fund 1 sold all of the 2,242,560 shares of Common Stock allocated to Valeant USA. Pershing Square has informed the Reporting Persons that

Exhibit 99.2 (supplied by Pershing Square) describes all transactions in shares of Common Stock and options or other derivatives relating to shares of Common Stock effected by Pershing Square in the past 60 days.

Other than the transactions described above, no transactions in shares of the Common Stock or options or other derivatives relating to shares of the Common Stock were effected by the Reporting Persons or, to the knowledge of the Reporting Persons, any of the other persons named in Item 2 of the Schedule 13D during the sixty days prior to the date of this Amendment No. 9.

(e) As of November 20, 2014, the Reporting Persons ceased to beneficially own more than 5% of the outstanding shares of Common Stock.

Item 6 of the Original 13D is hereby amended and supplemented by adding the following information:

The description of the November 20 Agreement set forth above is incorporated by reference into this Item 6 as if restated in full herein.

SIGNATURE

After reasonable inquiry and to the best of our knowledge and belief, we certify that the information set forth in this amendment is true, complete and correct.

Dated: November 20, 2014

EXHIBIT INDEX

Exhibit 99.1

November 20, 2014

Pershing Square Capital Management, L.P.

888 Seventh Avenue, 42^nd Floor

New York, New York 10019

Attention: William A. Ackman

Mr. Ackman:

Reference is made to (i) that certain letter agreement, dated as of February 9, 2014 (the “Confidentiality Agreement”), between Pershing Square Capital Management, L.P. (together with its controlled affiliates, and including any successor thereto, “you” or “Pershing Square”) and Valeant Pharmaceuticals International, Inc. (together with its controlled affiliates, and including any successor thereto, the “Company”), (ii) that certain letter agreement, dated as of February 25, 2014 and as amended May 30, 2014 (the “February 25 Agreement”), between Pershing Square and the Company executed in connection with a potential transaction related to Allergan, Inc. (“Allergan”) and (iii) the Amended and Restated LLC Agreement of PS Fund 1, LLC, dated as of April 3, 2014 (the “LLC Agreement”) entered into in connection with the February 25 Agreement. Capitalized terms used in this letter agreement (this “Agreement”) but not defined herein shall have the meanings given to such terms in the February 25 Agreement.

1. Sale of Company Allocated Sales. Pershing Square has caused PS Fund 1, LLC (“PS 1”) to sell 597,431 shares of Allergan Common Stock (the “Company Allocated Shares”) for the benefit of the Company.

2. Net Transaction Profits. In respect of the Company’s Net Transaction Profits, PS 1 has allocated to Valeant USA 1,645,129 shares of Allergan Common Stock (the “Company Profit Shares”) (based on the Company’s entitlement to Net Transaction Profits equal to $344,160,930 at a price per share of Allergan Common Stock of $209.20), with respect to which, as of the date hereof, all economic benefits and burdens have been allocated exclusively to Valeant USA. As such, the Company hereby irrevocably instructs Pershing Square to cause PS 1 to sell such Company Profit Shares as soon as

reasonably practicable for the benefit of Valeant USA. Pershing Square hereby agrees and acknowledges that no shares of Allergan Common Stock shall be sold by PS 1 until all of the Company Allocated Shares and the Company Profit Shares have been sold. In addition, the Company Profit Shares and the Company Allocated Shares have been hereby identified on the books and records of PS 1 based on the relevant tax lot numbers as follows: (a) Company Allocated Shares having tax lot date February 25, 2014 and February 26, 2014, and (b) Company Profit Shares having tax lot date May 1, 2014.

3. Payment.

(a) In making such sales of the Company Allocated Shares and Company Profit Shares, Pershing Square and PS 1 sought and shall in good faith seek to obtain the highest price possible for the Company Allocated Shares and Company Profit Shares and shall seek to minimize any transaction costs related to such sales of the Company Allocated Shares and Company Profit Shares to the extent that minimizing such costs does not affect obtaining the optimal price for the Company Allocated Shares and Company Profit Shares.

(b) Pershing Square shall cause PS 1 to pay to Valeant Pharmaceuticals International (“Valeant USA”) by wire transfer of immediately available funds to the account set forth on Schedule 1 hereto within four business days of the date hereof with respect to the sale of all of the Company Allocated Shares and within four business days of the sale of any Company Profit Shares, the proceeds of the sales of the Company Allocated Shares and Company Profit Shares (net of any out of pocket costs paid to third parties necessarily incurred in connection with such sales) together with all income attributable to such shares (including any declared, but unpaid dividends) since their purchase by or on behalf of PS 1.

4. PS Fund 1 Membership. Upon the allocation of the Company Profit Shares pursuant to Section 2 hereof, Valeant USA shall no longer be a member of PS 1 and the Company, Valeant USA and their affiliates shall have no further interest in PS 1 (except the right to be paid as required by Section 3(b) hereof). Valeant acknowledges and agrees for itself and on behalf of each of its controlled affiliates that following payment of all amounts owed hereunder, Pershing Square may amend the LLC Agreement in any manner it deems fit; provided that such amendments do not adversely affect any rights Valeant USA may have under Sections 16 and 17 of the LLC Agreement.

5. Settlement of Accounts. The allocation of the Company Profit Shares pursuant to Section 2 hereof and the payment of the aggregate amounts set forth in Sections 1, 2 and 3(b) hereunder shall be in full satisfaction of all of Pershing Square’s and PS 1’s payment obligations under Section 3 under the February 25 Agreement and in full satisfaction of any related payment obligations with respect to the Company’s capital

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account, share of Net Transaction Profits and any capital contributions to or distributions from PS 1 or any other payment obligations under the LLC Agreement. The parties hereto further agree that Section 1(e) of the February 25 Agreement shall terminate and be of no further force or effect. The Company hereby acknowledges that all of its rights under Section 3 of the February 25 Agreement are rights of Valeant USA and that no amounts are owed thereunder to any entity other than Valeant USA or to the Company.

6. Cooperation. Each of Pershing Square and the Company agree to cooperate with each other in connection with the litigation in the Federal District Court of California (Case Number 14-cv-01214), Allergan, Inc. et al. v. Valeant Pharmaceuticals International, Inc. et al., and any other claims arising from, relating to, or in connection with the facts giving rise to such litigation, and the parties shall bear their respective fees, costs and liabilities, if any, relating to any such claims.

7. Miscellaneous.

(a) This Agreement, the Confidentiality Agreement, the February 25 Agreement, and the LLC Agreement constitute the entire agreement among the parties hereto pertaining to the subject matter hereof and supersede all prior and contemporaneous agreements and understandings of the parties in connection therewith. Where the terms of this Agreement conflict with the Confidentiality Agreement, the February 25 Agreement, and/or the LLC Agreement, the terms of this Agreement shall govern.

(b) Sections 5(a), (c), (d), (e), (f), (g), (h) and (i) of the Confidentiality Agreement shall apply to this Agreement, mutatis mutandis.

(c) This Agreement may be executed in one or more counterparts, each of which shall be deemed an original, and all of which shall constitute one and the same Agreement.

[The next page is the signature page]

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If you are in agreement with the foregoing, please so indicate by signing and returning one copy of this Agreement, whereupon this Agreement will constitute our agreement with respect to the subject matter hereof.

CONFIRMED AND AGREED TO:

Dated: November 20, 2014

PS FUND 1, LLC

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Exhibit 99.2