UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)*

The Macerich Company

(Name of Issuer)

Common Stock, Par Value $0.01 Per Share

(Title of Class of Securities)

554382101

(CUSIP Number)

Jeff Davis

Senior Vice President and General Counsel

Ontario Teachers’ Pension Plan Board

5650 Yonge Street, 3rd Floor

Toronto, Ontario M2M 4H5

Canada

(416) 228-5900

With a Copy to:

William G. Farrar

Sullivan & Cromwell LLP

125 Broad Street

New York, New York 10004

(212) 558-4940

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

August 8, 2016

(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 (the “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).

SCHEDULE 13D

SCHEDULE 13D

This Amendment No. 4 (this “Amendment No. 4”) amends and supplements the statement on Schedule 13D filed with the Securities and Exchange Commission (the “SEC”) on November 24, 2014 (the “Original Schedule 13D”), Amendment No. 1 to the Original Schedule 13D filed with the SEC on May 8, 2015 (“Amendment No. 1”), Amendment No. 2 to the Original Schedule 13D filed with the SEC on May 15, 2015 (“Amendment No. 2”) and Amendment No. 3 to the Original Schedule 13D filed with the SEC on March 9, 2016 (“Amendment No. 3”, and together with the Original Schedule 13D, Amendment No. 1, Amendment No. 2 and this Amendment No. 4, the “Schedule 13D”) with respect to the common stock, par value $0.01 per share (the “Common Stock”), of The Macerich Company, a Maryland corporation (the “Issuer”), filed by Ontario Teachers’ Pension Plan Board, an Ontario, Canada corporation (“Teachers’”), and 1700480 Ontario Inc., an Ontario, Canada corporation (“1700480”), wholly owned by Teachers’. Capitalized terms used herein and not otherwise defined have the meanings assigned to such terms in the Original Schedule 13D. All items or responses not described herein remain as previously reported in the Original Schedule 13D, as amended and supplemented by Amendment No. 1, Amendment No. 2 and Amendment No. 3.

All calculations with respect to beneficial ownership of the Issuer’s Common Stock set forth in this Schedule 13D are based on 143,625,500 shares of Common Stock outstanding as of August 2, 2016, as reported on the cover of the Issuer’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2016, filed with the SEC by the Issuer on August 3, 2016 (the “June 2016 Form 10-Q”). Based on information reported by the Issuer in the June 2016 Form 10-Q, the Issuer repurchased 5,930,209 shares of its Common Stock between April 19, 2016 and July 11, 2016. The Issuer’s repurchases resulted in the increase in beneficial ownership of the Reporting Persons reported in this Amendment No. 4 from 15.6% in Amendment No. 3 to 16.2%.

Item 2 of the Schedule 13D is hereby amended solely with respect to Schedule A attached hereto.

Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following immediately prior to the last paragraph thereof:

On August 8, 2016, the Issuer, Teachers’ and 1700480 executed an agreement (the “Letter Agreement”) that: (i) amended the Limited Waiver to change the “Excepted Holder Limit” from 14.9% to 19.9% and to provide that, if Teachers’ Beneficial Ownership does not equal or exceed 19.7% at any time on or prior to July 31, 2021, then from and after that date the Excepted Holder Limit automatically will be reset to the highest Beneficial Ownership percentage actually reached by Teachers between August 1, 2016 and July 31, 2021; (ii) amended the Registration Rights Agreement to replace the definition of “Shares” with “all Common Shares directly or indirectly held from time to time by the Holders and their respective Affiliates”, and (iii) amended and restated Section 2.4 of the Master Agreement with the effect of replacing “9.9%” with “14.9%”

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in the two places it appears therein. A copy of the Letter Agreement is included as Exhibit 99.6 to this Schedule 13D and is incorporated by reference herein. The foregoing summary of the Letter Agreement is qualified in its entirety by reference to the full text of the Letter Agreement.

Paragraphs (a) and (b) of Item 5 of the Schedule 13D are hereby amended and restated in their entirety as follows:

(a) and (b). 1700480, as a wholly-owned subsidiary of Teachers’, may be deemed to share voting and dispositive power with Teachers’ with respect to the 23,286,237 shares of Common Stock it beneficially owns, representing approximately 16.2% of the shares of Common Stock outstanding. Pursuant to the Master Agreement, as amended by the Letter Agreement, 1700480 agreed that if it and its affiliates collectively own (beneficially or of record) more than 14.9% of the outstanding shares of Common Stock, 1700480 will cause to be voted in accordance with the recommendations of the Issuer’s Board of Directors all of the shares of Common Stock owned by them in excess of such number of shares that represents 14.9% of the outstanding shares of Common Stock. The foregoing summary of the Master Agreement, as amended by the Letter Agreement, is qualified in its entirety by reference to the full text of the Master Agreement and the full text of the Letter Agreement.

Item 6 of the Schedule 13D is hereby amended and supplemented by adding the following immediately prior to the last paragraph thereof:

On August 8, 2016, the Issuer, Teachers’ and 1700480 executed the Letter Agreement. See “Item 4. Purpose of Transaction” for a description of the Letter Agreement, which is qualified in its entirety by reference to the Letter Agreement, a copy of which is filed as Exhibit 99.6 hereto and incorporated herein by reference in answer to this Item 6.

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Signatures

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

August 9, 2016

SCHEDULE A

CERTAIN INFORMATION REGARDING THE BOARD MEMBERS AND OFFICERS

OF ONTARIO TEACHERS’ PENSION PLAN BOARD

Set forth in the table below are the name, current residence or business address and current occupation or employment of each of the board members and officers of Ontario Teachers’ Pension Plan Board, an Ontario, Canada corporation (“Teachers’”). Each director and officer is a citizen of Canada with the exception of: (i) Kathleen O’Neill who is a citizen of Canada and Ireland; (ii) Bjarne Graven Larsen who is a citizen of Denmark; and (iii) Andrew Jonathan Mark Taylor who is a citizen of the United Kingdom.

EXHIBIT INDEX

Exhibit 99.6

August 8, 2016

Ontario Teachers’ Pension Plan Board

c/o/The Cadillac Fairview Corporation Limited

20 Queen Street West, 5th Floor

Toronto, Ontario M5H 3R4

Attention: Sandra Hardy

Re: Amendment of Limited Waiver of Ownership Limit

Ladies and Gentlemen:

Reference is made to that certain Limited Waiver granted to Ontario Teachers’ Pension Plan Board and its affiliates (collectively, “Ontario”) by the Board of Directors (the “Board”) of The Macerich Company (“Macerich”) on November 14, 2014 (the “Waiver”), and the representation letter, dated as of November 14, 2014, entered into by Ontario and Macerich and attached to such Waiver, as amended on November 24, 2014 (the “Representation Letter”). Pursuant to the terms of the Waiver, among other matters, Ontario is currently permitted to Beneficially Own up to 14.9% of the Equity Stock of Macerich (or such other percentage as Ontario owns as a result of Macerich purchasing its own Equity Stock after the most recent date Ontario purchased additional Equity Stock). Capitalized terms used but not defined herein shall have the same meaning as set forth in Macerich’s charter (as amended to date).

The parties hereto desire to, and by execution of this letter agreement do, amend the Waiver and the Representation Letter and certain other documents as set forth herein.

“2.4 Voting Agreement. If 1700480 and its affiliates (as defined in the Securities Act of 1933, as amended (the “Securities Act”)), collectively own (beneficially or of record) greater than 14.9% of the outstanding shares of Macerich Common Stock, 1700480 shall cause to be voted in accordance with the recommendations of the Macerich board of directors such number of shares of Macerich Common Stock owned by 1700480 and such affiliates, taken together, equal to the difference of (a) the aggregate number of shares of Macerich Common Stock owned by 1700480 and its Affiliates minus (b) such number of shares that represents 14.9% of the outstanding shares of Macerich Common Stock. The obligations pursuant to this Section 2.4 will survive the Closing (as defined below), but automatically will expire and be of no further force or effect on the first date on which OTPP and its affiliates, including 1700480, no longer own a number of shares of Macerich Common Stock that exceeds the Ownership Limit (as defined in Macerich’s charter).”

All provisions of the Master Agreement other than Section 2.4 thereof remain in effect under their original terms and are not amended, modified or affected hereby.

“Shares” shall mean all Common Shares directly or indirectly held from time to time by the Holders and their respective Affiliates.”

[Remainder of Page Intentionally Left Blank]

IN WITNESS WHEREOF, the undersigned has executed this letter agreement as of the date first set forth above and agrees to be bound by the terms of this letter agreement.