UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

SiteOne Landscape Supply, Inc.

(Name of Issuer)

Common Stock, $0.01 par value

(Title of Class of Securities)

82982L 103

(CUSIP Number)

CD&R Landscapes Holdings, L.P.

c/o Clayton, Dubilier & Rice, LLC

Attention: Theresa A. Gore

375 Park Ave, New York NY 10152

(212) 407-5227

with a copy to

Peter J. Loughran, Esq.

Debevoise & Plimpton LLP

919 Third Avenue

New York, NY 10022

212-909-6000

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

July 27, 2017

(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 which is the subject of this Schedule 13D, and is filing this schedule because of Sections 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 Section 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).

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EXPLANATORY NOTE

The following constitutes Amendment No. 3 (“Amendment No. 3”) to the statement on Schedule 13D previously filed by the undersigned with the U.S. Securities and Exchange Commission (the “SEC”) on May 26, 2016 (the “Original 13D” and, as amended on December 7, 2016 and through the date hereof, the “Schedule 13D”). The Schedule 13D remains in full force and effect, except as specifically amended by this Amendment No. 3. The Schedule 13D is filed by the Reporting Persons as defined in Item 2 of the Original 13D. The Schedule 13D relates to shares of common stock, par value $0.01 (the “Common Stock”), of SiteOne Landscape Supply, Inc., a Delaware corporation (the “Issuer”). This Amendment No. 3 is being filed to reflect the sale of 3,545,091 shares of the Issuer’s Common Stock by the undersigned on July 26, 2017 (the “Sale”). All capitalized terms used but not defined herein shall have the meanings ascribed to such terms in the Original 13D.

Item 5 Interest in Securities of the Issuer

(a)

(i) CD&R Landscapes Holdings, L.P. is the beneficial owner of 0 shares of the Issuer’s Common Stock, representing 0% of the Issuer’s Common Stock, based on 39,739,351 shares of Common Stock outstanding as of the close of business on July 26, 2017.

(ii) CD&R Associates VIII, Ltd., as the general partner of CD&R Landscapes, may have been deemed to beneficially own the shares of Common Stock in which the CD&R Landscapes had beneficial ownership.

(iii) CD&R Associates VIII, L.P., as the sole stockholder of CD&R Associates VIII, Ltd., may have been deemed to beneficially own the shares of Common Stock in which CD&R Landscapes had beneficial ownership.

(iv) CD&R Investment Associates VIII, Ltd., as the general partner of CD&R Associates VIII, L.P., may have been deemed to beneficially own the shares of Common Stock in which CD&R Landscapes had beneficial ownership.

Each of CD&R Associates VIII, Ltd., CD&R Associates VIII, L.P. and CD&R Investment Associates VIII, Ltd. expressly disclaims beneficial ownership of the shares of the Issuer’s Common Stock in which CD&R Landscapes had beneficial ownership. CD&R Investment Associates VIII, Ltd. is managed by a two-person board of directors. Donald J. Gogel and Kevin J. Conway, as the directors of CD&R Investment Associates VIII, Ltd., may have been deemed to share beneficial ownership of the shares of the Issuer’s Common Stock in which CD&R Landscapes had beneficial ownership. Such persons expressly disclaim such beneficial ownership. Investment and voting decisions with respect to the shares of the Issuer’s Common Stock held by CD&R Landscapes are made by an investment committee of limited partners of CD&R Associates VIII, L.P., currently consisting of more than ten individuals (the “Investment Committee”). As of the date hereof, the investment professionals who have effective voting control of the Investment Committee are Michael G. Babiarz, Vindi Banga, James G. Berges, John C. Compton, Kevin J. Conway, Russell P. Fradin, Thomas C. Franco, Kenneth A. Giuriceo, Donald J. Gogel, Jillian Griffiths, Marco Herbst, Sarah Kim, John Krenicki, Jr., David A. Novak, Paul S. Pressler, Roberto Quarta, Christian Rochat, Ravi Sachdev, Steven W. Shapiro, Richard J. Schnall, Nathan K. Sleeper, Derek Strum, Sonja Terraneo, David H. Wasserman and J.L. Zrebiec. All members of the Investment Committee expressly disclaim beneficial ownership of the shares of the Issuer’s Common Stock that were beneficially owned by CD&R Landscapes.

(v) Neither the filing of this Schedule 13D nor any of its contents shall be construed as an admission that any of the Reporting Persons is, for the purpose of Section 13(d) of the Exchange Act, the beneficial owner of the Issuer’s Common Stock other than those which are directly held by CD&R Landscapes as of the date hereof.

(vi) Except as described in Sections (a)(i) – (iv) of this Item 5, no other person is a beneficial owner of the Issuer’s Common Stock in which CD&R Landscapes has direct beneficial ownership.

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(b) In addition to the description set forth above in this Item 5(a), see the cover pages of this Schedule 13D for indications of the respective voting powers and disposition powers of the Reporting Persons.

(c) On July 26, 2017, CD&R Landscapes sold in an underwritten secondary public offering 3,545,091 shares of Common Stock.

The response to Item 6 of this Schedule 13D is incorporated herein by reference.

(d) Not applicable.

(e) On July 26, 2017, following the transaction set forth herein, each of the Reporting Persons ceased to be the beneficial owner of more than five percent of the shares of Common Stock.

Item 6 Contracts, Arrangements, Understandings or Relationships with respect to Securities of the Issuer

Amended and Restated Stockholders Agreement

Upon the closing of the Sale, the Stockholders Agreement was automatically terminated.

Registration Rights Agreement

Upon the closing of the Sale, the Registration Rights Agreement was automatically terminated, except that certain indemnification obligations set forth in the Registration Rights Agreement survived termination.

Indemnification Agreement

The Issuer and certain of its wholly-owned subsidiaries are party to an Indemnification Agreement, dated December 23, 2013 (the “Indemnification Agreement”), with CD&R Landscapes and certain of its affiliates pursuant to which they each indemnify CD&R Landscapes and its affiliates, directors, officers, partners, members, employees, agents, representatives and controlling persons, against certain claims and liabilities, including liabilities arising out of financing arrangements and securities offerings.

The foregoing description of the Indemnification Agreement does not purport to be complete and is qualified in its entirety by reference to the Indemnification Agreement, which is filed as an exhibit and incorporated herein by reference.

Lock Up Agreement

CD&R Landscapes has signed a lock-up letter agreement (the “Lock-Up Agreement”) under which it has agreed, subject to certain exceptions, that, without the prior written waiver of two of the Representatives (as defined therein), it will not, during the period ending 45 days after July 20, 2017, offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale or otherwise dispose of any shares of the Issuer’s Common Stock, or any options or warrants to purchase any shares of the Issuer’s Common Stock, or any securities convertible into, exchangeable for or that represent the right to receive shares of the Issuer’s Common Stock.

The foregoing description of the Lock-Up Agreement does not purport to be complete and is qualified in its entirety by reference to the Lock-Up Agreement, which is filed as an exhibit and incorporated herein by reference.

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Item 7 Material to be Filed as an Exhibit.

Exhibit 7.1: Joint Filing Agreement, dated July 27, 2017, by and between CD&R Landscapes Holdings, L.P., CD&R Associates VIII, Ltd., CD&R Associates VIII, L.P. and CD&R Investment Associates VIII, Ltd.

Exhibit 7.2: Amended and Restated Stockholders Agreement of SiteOne Landscape Supply, Inc., dated May 12, 2016, by and among SiteOne Landscape Supply, Inc., CD&R Landscapes Holdings, L.P. and Deere & Company, incorporated by reference to Exhibit 7.2 to the Original 13D (No. 005-89511).

Exhibit 7.3: Registration Rights Agreement of SiteOne Landscape Supply, Inc. (f/k/a CD&R Landscapes Parent, Inc.), dated as of December 23, 2013, by and among SiteOne Landscape Supply, Inc., CD&R Landscapes Holdings, L.P. and Deere & Company, incorporated by reference to Exhibit 10.3 to the Issuer’s Registration Statement on Form S-1 (No. 333-206444).

Exhibit 7.4: Indemnification Agreement, dated as of December 23, 2013, by and among SiteOne Landscape Supply, Inc. (f/k/a CD&R Landscapes Parent, Inc.), SiteOne Landscape Supply Midco, Inc. (f/k/a CD&R Landscapes Midco, Inc.), SiteOne Landscape Supply Bidco, Inc. (f/k/a CD&R Landscapes Bidco, Inc.), SiteOne Landscape Supply Holding, LLC (f/k/a JDA Holding LLC), SiteOne Landscape Supply, LLC (f/k/a John Deere Landscapes LLC ), CD&R Landscapes Holdings, L.P., Clayton, Dubilier & Rice Fund VIII, L.P., CD&R Friends & Family Fund VIII, L.P., CD&R Advisor Fund VIII Co-Investor, L.P., Clayton. Dubilier & Rice Inc., and Clayton, Dubilier & Rice, LLC, incorporated by reference to Exhibit 10.8 to the Issuer’s Registration Statement on Form S-1 (No. 333-206444).

Exhibit 7.5: Lock-Up Letter Agreement, dated July 20, 2017, executed by CD&R Landscapes Holdings, L.P.

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Signature

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.

Date: July 27, 2017

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Exhibit 7.1

JOINT FILING AGREEMENT

Pursuant to Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned agree that the Statement on Schedule 13D to which this exhibit is attached is filed on behalf of each of them in the capacities set forth below.

Date: July 27, 2017

Exhibit 7.5

SiteOne Landscape Supply, Inc.

Lock-Up Agreement

July 20, 2017

Deutsche Bank Securities Inc.

60 Wall Street

New York, New York 10005

Ladies and Gentlemen:

The undersigned understands that you, as underwriter (the “Underwriter”), propose to enter into an Underwriting Agreement (the “Underwriting Agreement”), with SiteOne Landscape Supply, Inc., a Delaware corporation (the “Company”), and the Selling Stockholders named in Schedule I to such agreement, providing for a public offering (the “Public Offering”) of shares (the “Shares”) of common stock, $0.01 par value per share (the “Stock”) of the Company, pursuant to a Registration Statement on Form S-3 (File No. 333-219370) filed with the U.S. Securities and Exchange Commission (the “SEC”).

In consideration of the agreement by the Underwriter to offer and sell the Shares, and of other good and valuable consideration the receipt and sufficiency of which is hereby acknowledged, the undersigned agrees that, subject to the other provisions of this Lock-Up Agreement, during the period specified in the following paragraph (the “Lock-Up Period”), the undersigned will not, without having received a prior written waiver from the Underwriter (the “Lock-Up Waiver Requirement”), (i) offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale or otherwise dispose of any shares of Stock of the Company, or any options or warrants to purchase shares of Stock, shares acquired upon the vesting of restricted stock units or settlement of deferred stock units or any securities that are convertible into or exchangeable for, or that represent the right to receive, Stock (collectively the “Undersigned’s Shares”) (other than the sale, transfer or other disposition of any shares of Stock acquired after the Public Offering Date (as defined below) that is not required to be reported in any public report or filing with the SEC and regarding which the undersigned does not otherwise voluntarily effect any public filing or report), the foregoing restriction being expressly agreed to preclude the undersigned from engaging in any hedging or other transaction which is designed to or which reasonably could be expected to lead to or result in a sale or disposition or the Undersigned’s Shares even if such Shares would be disposed of by someone other than the undersigned, or (ii) enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of the Undersigned’s Shares.

The Lock-Up Period will commence on the date of the preliminary prospectus first used in connection with the offering of Shares and continue for 45 days after the public offering date set forth on the final prospectus (the “Public Offering Date”) pursuant to the Underwriting Agreement.

Notwithstanding the foregoing, the undersigned may transfer the Undersigned’s Shares without having received any waiver in compliance with the Lock-Up Waiver Requirement; provided that (1) any such transfer shall not involve a disposition for value (other than those described below in (i), (ii), (v) and (vii)), (2) such transfers (other than those described below in (i) and (vii)) are not required to be reported with the SEC on Form 4 in accordance with Section 16 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and (3) the undersigned does not otherwise voluntarily effect any public filing or report regarding such transfers:

(i) as sales to the Underwriter pursuant to the Underwriting Agreement; or

(ii) any transfer pursuant to a bona fide third party tender offer, merger, consolidation or other similar transaction made to all holders of the Stock involving a change of control of the Company; or

(iii) as a bona fide gift or gifts; or

(iv) by will or intestacy; or

(v) to any trust for the direct or indirect benefit of the undersigned or the immediate family of the undersigned (for purposes of this lock-up agreement, “immediate family” shall mean any relationship by blood, marriage or adoption, not more remote than first cousin); or

(vi) to the undersigned’s partners, members or shareholders, subsidiaries, affiliates or to any investment fund or other entity controlled or managed by, or under common control or management with, the undersigned; or

(vii) dispositions of shares of Stock to the Company or the retention of shares of Stock by the Company (i) to satisfy tax withholding obligations in connection with the exercise of options to purchase Stock, the vesting of restricted stock units or the settlement of deferred stock units or (ii) in payment of the exercise or purchase price with respect to the exercise of options to purchase Stock, the vesting of restricted stock units or the settlement of deferred stock units; or

(viii) transfers of shares of Stock by the undersigned in connection with bona fide gifts of such shares of Stock to charitable organizations by certain partners and employees of the undersigned, its affiliates or any investment fund or other entity controlled or managed by, or under common control or management with, the undersigned;

provided, however, that in the case of clauses (iii)-(vi) and (viii), the Underwriter shall have received a signed lock-up agreement for the balance of the Lock-Up Period from each donee, trustee, distributee, or transferee, as the case may be, prior to such transfer; and provided, further, that nothing in this agreement shall prevent the establishment of a

trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer or purchase of shares of Stock; provided that such plan (a) does not provide for the transfer of Stock during the Lock-Up Period, and (b) is not required to be reported and is not voluntarily reported in any public report or filing with the SEC during the Lock-Up Period.

The undersigned also agrees and consents to the entry of stop transfer instructions with the Company’s transfer agent and registrar against the transfer of the Undersigned’s Shares except in compliance with the foregoing restrictions.

The undersigned understands that the Company, the Selling Stockholders and the Underwriter are relying upon this Lock-Up Agreement in proceeding toward consummation of the offering. The undersigned further understands that this Lock-Up Agreement is irrevocable and shall be binding upon the undersigned’s heirs, legal representatives, successors, and assigns.

[Signature Page to Lock-up Agreement]