UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No.          )

IRON MOUNTAIN INCORPORATED
NOTICE OF 20162017 ANNUAL MEETING OF STOCKHOLDERS
TO BE HELD ON JUNE 17, 2016
MAY 24, 2017

To the Stockholders of
IRON MOUNTAIN INCORPORATED:

        Iron Mountain Incorporated will hold its 20162017 Annual Meeting of Stockholders, or the Annual Meeting, at the offices of Sullivan & Worcester LLP, One Post Office Square, 21st Floor, Boston, Massachusetts 02109, on June 17, 2016,May 24, 2017, at 10:9:00 a.m. local timeU.S. Eastern Time (11:00 p.m. Australian Eastern Standard Time on May 24, 2017) for the following purposes:

1.

To elect twelve (12) directors to the Board of Directors of Iron Mountain Incorporated for a one-year term as directors or until their successors are elected and qualified;



2.

To approve an amendment to the Iron Mountain Incorporated 2014 Stock and Cash Incentive Plan, or the 2014 Plan, to increase the number of shares of Common Stock authorized for issuance thereunder by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value (as defined in the 2014 Plan) as of the date such award is granted;



3.

To hold a non-binding, advisory vote on the compensation of Iron Mountain Incorporated's Named Executive Officers as described in the accompanying Proxy Statement;



3.4.

To hold a non-binding, advisory vote on the frequency (every one, two or three years) of future advisory votes of stockholders on the compensation of Iron Mountain Incorporated's Named Executive Officers;



5.

To ratify the selection by the Audit Committee of Deloitte & Touche LLP as Iron Mountain Incorporated's independent registered public accounting firm for the year ending December 31, 2016;2017; and



4.6.

To transact such other business as may properly come before the Annual Meeting.

        Attached to this notice is a Proxy Statement relating to the proposals to be considered at the Annual Meeting. The Board of Directors has fixed the close of business on April 20, 20164, 2017 (5:00 p.m., U.S. Eastern Time) as the record date, or the Record Date, for the determination of stockholders entitled to receive notice of and to vote at the Annual Meeting or at any adjournment or postponement thereof. Record holders of CHESS Depositary Interests, or CDIs, as of 5:00 p.m., U.S. Eastern Time (7:00 a.m. Australian Eastern Standard Time), on the Record Date are entitled to receive notice of and attend the Annual Meeting or any adjournment or postponement thereof but may not vote in person at the Annual Meeting. This Proxy Statement is dated April 26, 2016.13, 2017.

        United States Securities and Exchange Commission rules allow us to furnish proxy materials to our stockholders on the internet. YouStockholders can now access proxy materials and vote at www.proxyvote.com. YouStockholders may also vote via internet or telephone by following the instructions on that website. In order to vote on the internet or by telephone, youstockholders must have a stockholder identification number, which is being mailed to youstockholders on a Notice Regarding the Availability of Proxy Materials.

        CDI holders may vote the shares of our common stock underlying their CDIs by instructing our CDI Depositary, CHESS Depositary Nominees Pty Ltd, or CDN. Each CDI holder may instruct CDN to vote on behalf of such CDI holder at the Annual Meeting by either following the instructions on the CDI voting instruction form or by voting online at www.linkmarketservices.com.au. CDI holders may instruct CDN to vote on their behalf only by completing and signing the CDI voting instruction form or voting online at www.linkmarketservices.com.au.

        YOUR VOTE IS IMPORTANT REGARDLESS OF THE NUMBER OF SHARES THAT YOU BENEFICIALLY OWN.    We urge you to read the Proxy Statement carefully and, whether or not you plan to attend the Annual Meeting, to castvote your shares (or direct CDN to vote if you hold your shares in the form of CDIs) without delay as instructed inonline, by telephone (if you are a stockholder) or by mailing a completed proxy card or CDI voting instruction form if you elect to receive the Notice Regardingproxy materials by mail. Instructions regarding each method of voting are provided on the Availability of Proxy Materials that you receive inproxy card and the mail.CDI voting instruction form. You may also request a paper proxy card or CDI voting instruction form at any time on or before June 3, 2016May 10, 2017 to submit your vote by mail. Proxies may be revoked, or the votes reflected in the proxy changed, by (1) delivering written notice or another duly executed proxy bearing a later date to the Secretary of Iron Mountain Incorporated, (2) completing another proxy in the same manner indicated on the website referred to in the Notice Regarding the Availability of Proxy Materials or (3) attending the Annual Meeting and voting in person. If you hold shares in the name of a brokerage firm, bank, nominee or other institution, you must provide a legal proxy from that institution in order to vote your shares at the Annual Meeting, except as otherwise discussed in the Proxy Statement.

        All stockholders and CDI holders are cordially invited to attend the Annual Meeting.

Boston, Massachusetts
April 13, 2017

        IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE 2017 ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON JUNE 17, 2016:STOCKHOLDERS: This Notice of Annual Meeting and Proxy Statement, Iron Mountain Incorporated's Annual Report to Stockholders for the year ended December 31, 20152016 and directions to the Annual Meeting are available at: www.materials.proxyvote.com/https://materials.proxyvote.com/46284v. If you are a CDI holder, you may also view and print these materials online at www.linkmarketservices.com.au.

IRON MOUNTAIN INCORPORATED
PROXY STATEMENT
FOR THE 20162017 ANNUAL MEETING OF STOCKHOLDERS

To be held on June 17, 2016May 24, 2017

GENERAL INFORMATION

        This Proxy Statement is furnished in connection with the solicitation of proxies by the Board of Directors, or the Board, of Iron Mountain Incorporated, or Iron Mountain, the Company, we, us or our, for use at the Annual Meeting of Stockholders to be held at 9:00 a.m. U.S. Eastern Time on June 17, 2016,May 24, 2017 (11:00 p.m. Australian Eastern Standard Time on May 24, 2017), or the Annual Meeting, or at any adjournment or postponement thereof. All stockholders and holders of CHESS Depositary Interests, or CDIs, of record on April 20, 20164, 2017 (5:00 p.m. U.S. Eastern Time), or the Record Date, are invited to attend the Annual Meeting. The Company's Annual Report to Stockholders for the year ended December 31, 2015 and2016, the Notice Regarding the Availability of Proxy Materials relating to the Annual Meeting, or the Notice of Internet Availability, and, in the case of CDI holders, the CDI voting instruction form, is first being mailed to the Company's stockholders ofin the CompanyUnited States on or about April 26, 2016.13, 2017 and to CDI holders in Australia on or about April 18, 2017 (which is the next business day in Australia following the mailing in the United States).

        The Company will bear all costs of solicitation of proxies. Brokers, banks, custodians and other fiduciaries will be requested to forward proxy solicitation materials to the beneficial owners of shares held of record by such persons, and the Company will reimburse thembrokers, banks, custodians and other fiduciaries for their reasonable out-of-pocket expenses incurred in connection with the distribution of such proxy solicitation materials. Solicitation of proxies by mail may be supplemented by telephone, telecopier or personal solicitation by directors, officers or other regular employees of the Company (who will not receive any additional compensation for any solicitation of proxies).

        The Board unanimously recommends that you vote:

•

FOR the election of each of the Board's nominees for director;



•

FOR the approval of an amendment to the Iron Mountain Incorporated 2014 Stock and Cash Incentive Plan, or the 2014 Plan, to increase the number of shares of Common Stock authorized for issuance thereunder by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value (as defined in the 2014 Plan) as of the date such award is granted;



•

FOR the approval of a non-binding, advisory resolution approving the compensation of the Named Executive Officers as described in this Proxy Statement;



•

To hold a non-binding, advisory vote on the frequency of future advisory votes of stockholders on the compensation of the Named Executive Officers EVERY YEAR; and



•

FOR the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the year ending December 31, 2016.2017.

Stockholders and CDI Holders Entitled to Vote

        Iron Mountain's common stock, $0.01 par value per share, or the Common Stock, is the only class of voting securities outstanding and entitled to vote at the Annual Meeting. Shares of Common Stock also

trade on the Australian Stock Exchange, or ASX, in the form of CDIs. Each CDI represents a beneficial interest in one share of Common Stock. As of the close of business5:00 p.m. U.S. Eastern Time on April 20, 2016, the record date for the determination of stockholders entitled to notice of and to vote at the Annual Meeting, or the Record Date, 211,946,343264,103,202 shares of Common Stock (including 17,129,594 CDIs exchangeable into shares of Common Stock) were outstanding and entitled to vote. Each share of Common Stock is entitled to one vote on each matter.

How to Vote

        Your vote is very important no matter how many shares of Common Stock or CDIs you own. Whether or not you plan to attend the Annual Meeting, we urge you to vote your shares or CDIs today.

        If youStockholders who wish to receive a paper or email copy of the proxy card to complete and mail to the Company in time for the Annual Meeting you may request one at any time on or before June 3, 2016. YouMay 10, 2017. Stockholders may vote yourtheir shares over the internet or by telephone in the manner provided on the website indicated in the Notice of Internet Availability youthey receive in the mail, or the Website, by completing and returning a proxy card or by attending the Annual Meeting and voting in person. CDI holders may instruct our CDI Depositary, CHESS Depositary Nominees Pty Ltd, or CDN, to vote on their behalf only by completing and signing the CDI voting instruction form or voting online at www.linkmarketservices.com.au. Votes provided over the internet or by telephone by stockholders must be received by 11:59 p.m. U.S. Eastern Daylight Time on June 16, 2016.May 23, 2017, and instructions provided over the internet by our CDI holders must be received by 1:59 p.m. Australian Eastern Standard Time on May 22, 2017).

If You Are a Registered Holder of Common Stock

        If you are a registered holder of Common Stock, you may vote your shares either by voting by proxy in advance of the Annual Meeting or by voting in person at the Annual Meeting. By submitting a proxy (on a proxy card or in the manner provided on the Website), you are legally authorizing another person to vote your shares on your behalf. We urge you to vote (1) FOR the Board's nominees for director, (2) FOR the approval of a non-binding, advisory resolution approving the compensation of our Named Executive Officers as described in this Proxy Statement and (3) FOR the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the year ending December 31, 2016. If you submit your executed proxy card or submit a proxy in the manner provided on the Website, your shares will be voted in accordance with the Board's recommendations set forth in this Proxy Statement, unless otherwise directed, in which case your shares will be voted as specified by you on the proxy. In addition, if any other matters are brought before the Annual Meeting (other than the proposals contained in this Proxy Statement), then the individuals listed on the proxy will have the authority to vote your shares on those other matters in accordance with their discretion and judgment.

        In case a quorum is not present at the Annual Meeting, the holders of a majority of the voting power of the shares present at the Annual Meeting in person or represented by proxy may adjourn the Annual Meeting (without notice other than announcement of adjournment at the Annual Meeting) to another time, or to another time and place.

        Whether or not you plan to attend the Annual Meeting, we urge you to promptly vote over the internet or by telephone in the manner provided on the Website or by completing and returning a proxy card. If you later decide to attend the Annual Meeting and vote in person, the vote you cast in person at the Annual Meeting will automatically revoke any previously submitted proxy.

If You Hold Your Shares of Common Stock "In Street Name"

        If your shares are held in the name of a brokerage firm, bank, nominee or other institution (referred to as "in street name"), you will receive instructions from the holder of record, or street name holder, that you must follow in order for you to specify how your shares will be voted. If you do not specify how you would like your shares to be voted, your shares held in street name may still be voted. Certain street name holders have the authority to vote shares for which their customers do not

provide voting instructions on certain routine, uncontested items.proposals. The election of directors, the vote to approve the amendment to the 2014 Plan and the advisory votevotes on executive compensation and the frequency of future advisory votes of stockholders on executive compensation are not routine matters for purposes of broker voting. The ratification of the selection of our independent registered public accounting firm for the fiscal year ending December 31, 20162017 is a routine matter; therefore, there will be no broker non-votes in connection with that matter.

        IMPORTANT: If your shares are held in the name of a brokerage firm, bank, nominee or other institution, you should provide instructions to your broker, bank, nominee or other institution on how to vote your shares. Please contact the person responsible for your account and give instructions for a proxy to be completed for your shares.

If You Hold CDIs

        Each CDI holder is entitled to direct CDN to cast one vote for each CDI held by such holder. CDI holders are entitled to receive notice of and attend the Annual Meeting and any adjournment or postponement thereof and may direct CDN to vote their underlying shares of Common Stock at the Annual Meeting by (1) returning a validly completed CDI voting instruction form to Link Market Services Limited, Locked Bag A14, Sydney South, New South Wales, Australia 1235, the agent we designated for the collection and processing of voting instructions from our CDI holders, so that it is received by no later than 1:59 p.m. Australian Eastern Standard Time on May 22, 2017 (which is 11:59 p.m. U.S. Eastern Time on May 21, 2017) or (2) voting online at www.linkmarketservices.com.au before the termination time and date.

        Alternatively, any CDI holder may inform Iron Mountain that such CDI holder wishes to nominate himself or another person to be appointed as CDN's proxy with respect to such CDI holder's underlying shares of Common Stock for the purposes of attending and voting at the Annual Meeting. Holders of CDIs will not appear on Iron Mountain's share register as the legal holders of Common Stock; therefore, CDI holders will not be entitled to vote at the Annual Meeting unless they are appointed as proxy by CDN.

Quorum

        The presence at the Annual Meeting, in person or by proxy, of stockholders entitled to cast at least a majority of the votes that all stockholders are entitled to cast at the Annual Meeting, including the shares represented by the CDIs, will constitute a quorum. Shares represented by valid proxies (in the case of stockholders) or valid CDI voting instruction forms (in the case of CDI holders) will be treated as present at the Annual Meeting for purposes of determining a quorum, without regard to whether the proxy is noted as casting a vote or abstaining. Shares represented by broker non-votes will be treated as present for purposes of determining a quorum. Shares voted by a broker on any issue other than a procedural motion will be considered present for all quorum purposes, even if the shares are not voted on every matter.

Votes Required

        As more fully described in this Proxy Statement:

•

Each nominee for director must receive a majority of the votes cast on his or her nomination to be elected;



•

Approval of an amendment to the 2014 Plan to increase the number of shares of Common Stock authorized for issuance thereunder by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related awards granted under

the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value (as defined in the 2014 Plan) as of the date such award is granted, requires affirmative vote of holders of a majority of the votes cast on the proposal;

•

Approval of a non-binding, advisory resolution approving the compensation of ourthe individuals listed in the Summary Compensation Table on page 75 of this Proxy Statement, or the Named Executive Officers as described in this Proxy Statement requires the affirmative vote of a majority of the votes cast on the proposal;



•

The frequency that receives the highest number of votes will be considered the frequency recommended by stockholders to hold a non-binding, advisory vote on the compensation of our Named Executive Officers; and



•

Approval of the proposal to ratify the selection of the Company's independent registered public accounting firm requires the affirmative vote of a majority of the votes cast on the proposal.

Abstentions and Broker Non-Votes

        A "broker non-vote" occurs on an itema proposal when a broker identified as the record holder of shares is not permitted by the rules of the New York Stock Exchange, or the NYSE, to vote on that itemproposal without instruction from the beneficial owner of the shares and no instruction has been received with respect to that item.proposal. Under the NYSE rules, brokers may vote on routine matters even without instructions from the street name holder. The election of directors, the vote to approve of the amendment to the 2014 Plan and the advisory votevotes on executive compensation and frequency of future advisory votes on executive compensation are not routine matters for purposes of broker voting. If you do not instruct your broker how to vote with respect to these items,proposals, your broker may not vote with respect to these proposals and your shares will be counted as "broker non-votes." The ratification of the selection of our independent registered public accounting firm for the fiscal year ending December 31, 20162017 is a routine matter; therefore, there will be no broker non-votes in connection with that matter. CDN is not permitted to cast votes on any proposal unless specifically directed by the applicable CDI holder.

        A properly completed proxy and CDI voting instruction form, if received in time for voting and not revoked, will be voted at the Annual Meeting in accordance with the instructions contained therein, and, unlesstherein. Unless otherwise directed, the shares represented by the proxy card will be voted:

•

"For" the election of the Board's nominees for director listed in this Proxy Statement;



•

"For" the approval of an amendment to the 2014 Plan to increase the number of shares of Common Stock authorized for issuance thereunder by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value (as defined in the 2014 Plan) as of the date such award is granted;



•

"For" the approval of a non-binding, advisory resolution approving the compensation of our Named Executive Officers as described in this Proxy Statement;



•

To hold a non-binding, advisory vote on the frequency of future advisory votes of stockholders on the compensation of our Named Executive Officers "every year"; and



•

"For" the ratification of the selection by the Audit Committee of Deloitte & Touche LLP as the Company'sour independent registered public accounting firm for the year ending December 31, 2016.2017.

        Abstentions and broker non-votes will not be counted as votes cast and, therefore, will not affect the proposals that are being submitted to the stockholders at the Annual Meeting.

        Although the advisory votevotes on the proposed resolutionresolutions to approve the compensation of the Company'sour Named Executive Officers isand on the frequency of future advisory votes of stockholders on the compensation of our Named Executive Officers are non-binding, the Compensation Committee of the Board will consider the outcome of the votethese votes when making future compensation decisions for our Named Executive Officers and when determining how frequently to hold a vote on the Company'scompensation of our Named Executive Officers.

Attendance at the Annual Meeting

        Attendance at the Annual Meeting or any adjournment or postponement thereof will be limited to stockholders and CDI holders of record of the Company as of the close of business5:00 p.m., U.S. Eastern Time, on the Record Date (7:00 a.m. Australian Eastern Standard Time on April 5, 2017) and guests of the Company. If you are a stockholder or CDI holder of record as of the close of business5:00 p.m., U.S. Eastern Time, on the Record Date (7:00 a.m. Australian Eastern Standard Time on April 5, 2017), your name will be verified against the list of stockholders or CDI holders, as applicable, of record prior to your admittance to the Annual Meeting or any adjournment or postponement thereof. Please be prepared to present photo identification for admission. If you hold your shares in street name, you will need to provide proof of beneficial ownership, such as a brokerage account statement, a copy of a voting instruction form

provided by your custodian with respect to the Annual Meeting or other similar evidence of ownership, as well as photo identification, in order to be admitted to the Annual Meeting. Please note that if you hold your shares in street name and intend to vote in person at the Annual Meeting, you must also provide a "legal proxy" obtained from your custodian. CDI holders may attend the Annual Meeting but cannot vote in person at the Annual Meeting unless they are appointed as proxy by CDN.

Revocability of Proxies

        Any stockholder giving a proxy in the manner set forth in the Notice of Internet Availability has the power to revoke such proxy at any time before it is exercised. If you are a registered holder of Common Stock, you may revoke a previously submitted proxy by voting over the internet or by telephone at a later time in the manner provided on the Website. Any such notice or vote must be received by 11:59 p.m. U.S. Eastern Daylight Time on June 16, 2016.May 23, 2017. You may also revoke your proxy by attending the Annual Meeting and voting in person.

        If you are a CDI holder and you direct CDN to vote by completing the CDI voting instruction form, you may revoke those directions online at www.linkmarketservices.com.au or by delivering to Link Market Services Limited, Locked Bag A14, Sydney South, New South Wales, Australia 1235, no later than 1:59 p.m. Australian Eastern Standard Time on May 22, 2017 (which is 11:59 p.m. U.S. Eastern Time on May 21, 2017).

Please note, however, that only your last-dated proxy or CDI voting instruction will count, and any proxy or CDI voting instruction may be revoked at any time prior to its exercise at the Annual Meeting, as described in this Proxy Statement.

        If your shares are held in the name of a brokerage firm, bank, nominee or other institution, and you have instructed your brokerage firm, bank, nominee or other institution to vote your shares, you must follow the instructions received from your brokerage firm, bank, nominee or other institution to change your voting instruction. Please contact your custodian for detailed instructions on how to revoke your voting instruction and the applicable deadlines.

        Our principal executive offices are located at One Federal Street, Boston, Massachusetts 02110.

        The Company's website address, www.ironmountain.com, is included several times in this Proxy Statement as a textual reference only, and the information in the Company's website is not incorporated by reference into this Proxy Statement.

Notice Regarding the Availability of Proxy Materials

        In accordance with rules and regulations of the Securities and Exchange Commission, or the SEC, instead of mailing a printed copy of our proxy materials to each stockholder of record, the Company may furnish proxy materials via the internet. Accordingly, all of the Company's stockholders will receive a Notice of Internet Availability, which will be mailed on or about April 26, 2016.13, 2017.

        On the date of mailing the Notice of Internet Availability, stockholders will be able to access all of the proxy materials at www.materials.proxyvote.com/https://materials.proxyvote.com/46284v. The proxy materials will be available free of charge, and the Notice of Internet Availability will provide instructions as to how youstockholders may access and review all of the important information contained in the proxy materials (including the Company's Annual Report to stockholders)Stockholders) over the internet or through other methods specified on the Website. The Website contains instructions as to how tostockholders may vote by internet or over the telephone. The Notice of Internet Availability also instructs youstockholders as to how youthey may request a paper or email copy of the proxy card. If you receive a Notice of Internet Availability and would like to receive printed copies of the proxy materials, you should follow the instructions for requesting such materials included in the Notice of Internet Availability.

        All CDI holders will receive a printed copy of our proxy materials along with the CDI voting instruction form. If you are a CDI holder, you may also view and print these materials online at www.linkmarketservices.com.au. The CDI voting instruction form will provide instructions as to how CDI holders may access and review all of the important information contained in the proxy materials (including the Company's Annual Report to Stockholders) over the internet. The CDI voting instruction form contains instructions as to how CDI holders may direct CDN to vote on their behalf.

ITEMPROPOSAL 1

ELECTION OF DIRECTORS

        The Board currently consists of ten (10)twelve (12) directors. Each current director servesserved for a one-year term, and the term of each director will expire at the Annual Meeting.

        In September 2015, in connection with the Company's agreement, or the Recall Agreement, to acquire Recall Holdings Limited, or Recall, and conditioned on the consummation of the Company's acquisition of Recall, the Board increased the number of directors to twelve (12) and appointed Mr. Neil Chatfield and Ms. Wendy J. Murdock, each of whom currently serves as a non-executive director of Recall, to the Board. In accordance with the terms of the Recall Agreement, the Board also agreed to name Mr. Chatfield and Ms. Murdock as nominees to the Board to be voted on by the Company's stockholders at the first annual meeting of stockholders following the consummation of the Company's acquisition of Recall. The Company expects to complete the acquisition of Recall on May 2, 2016, and, consequently, the appointment of Mr. Chatfield and Ms. Murdock to the Board is expected to become effective on May 2, 2016. The term of each of Mr. Chatfield and Ms. Murdock will expire at the Annual Meeting.

        At the Annual Meeting, all nominees are to be elected for a one-year termsterm to serve until the Company's 20172018 Annual Meeting of Stockholders, or until their successors are elected and qualified. The Board has selected as nominees the following twelve (12) individuals, all of whom are current directors of the Company (except for Mr. Chatfield and Ms. Murdock, each of whom is expected to become a director of the Company on May 2, 2016):Company: Jennifer Allerton, Ted R. Antenucci, Pamela M. Arway, Clarke H. Bailey, Neil Chatfield, Kent P. Dauten, Paul F. Deninger, Per-Kristian Halvorsen, William L. Meaney, Wendy J. Murdock, Walter C. Rakowich and Alfred J. Verrecchia. Each nominee has agreed to serve if elected, and management has no reason to believe that any of the nominees will be unavailable to serve.

Required Vote

        Each nominee for director must receive a majority of the votes cast on his or her nomination to be elected. This means a nominee will be elected to the Board only if the votes cast "For" such nominee's election exceed the votes cast "Against" such nominee's election, with abstentions and broker non-votes not counting as votes "For" or "Against." Under the Company's Bylaws, if the number of votes cast "For" a director nominee does not exceed the number of votes "Against" the director nominee, and if the nominee is an incumbent director, then he or she must promptly tender his or her resignation from the Board. Each incumbent director and each of Mr. Chatfield and Ms. Murdock, has already tendered an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the Annual Meeting or any meeting of stockholders at which he or she faces re-election and (2) the acceptance of such resignation by the Board. The Board will decide within 90 days of the certification of the stockholder vote, through a process managed by the Nominating and Governance Committee of the Board and excluding the nominee in question, whether to accept the resignation. The Board's explanation of its decision will be promptly disclosed in a filing with the SEC.

        Brokers and CDN are not permitted to vote your shares for the election of directors absent instruction from you. Therefore, we urge you to give voting instructions to your broker on the proxy, or, in the case of CDI holders, give valid directions to CDN, so that your votes may be counted on this important matter.

        The Board recommends that you vote FOR the election of each of the Board's twelve (12) nominees to serve as directors of Iron Mountain until the 20172018 Annual Meeting of Stockholders, or until their successors are elected and qualified.

Information Concerning the Directors and Director Nominees

        Set forth below is the name and age of each of our director nominees and his or her principal occupation as of April 15, 2016,6, 2017, as well as his or her business experience during the past five years and the names of certain other companies of which he or she currently serves as a director or has served as a director during the past five years. In addition to the information presented below regarding each nominee's specific experience, qualifications, attributes and skills that led our Board to the conclusion that he or she should serve as a director, we also believe that all of our director nominees have a reputation for integrity and sound judgment and excellent analytical skills. Each of our director nominees has demonstrated business acumen and complements the attributes and skills of the other

director nominees. Each of the nominees has consented to be named in this Proxy Statement and to serve on the Board, if elected.

        The Board annually elects the officers of the Company. Each officer holds office at the discretion of the Board until the first meeting of the Board following the next annual meeting of stockholders or until such officer sooner dies, resigns or is removed. There are no family relationships between or among any of the Company's officers or directors.

        Set forth below is the name and age of each of our executive officers who is not nominated to be a director of the Company, his or her principal occupation and business experience during the past five years and the names of certain other companies of which he or she served as a director, as of April 15, 2016.6, 2017.

Board of Directors and Committees

        Independence.    Our Board is composed of a majority of directors who qualify as independent directors pursuant to the corporate governance standards for companies listed on the NYSE. The Board evaluates independence pursuant to NYSE standards each year by affirmatively determining whether each director has a direct or indirect material relationship with the Company (including its subsidiaries) and members of the Company's management that may interfere with such director's ability to exercise his or her independence from the Company. When assessing the materiality of a director's relationship with the Company, the Board considers all relevant facts and circumstances, not merely from the director's standpoint but from that of the persons or organizations with which the director has an affiliation. Material relationships can include commercial, industrial, banking, consulting, legal, accounting, charitable and familial relationships. None of our independent directors (other than Mr. Deninger) has any relationship with the Company or its management other than his or her service as a director and on committees of the Board, and the Board has concluded that none of the Company's directors possess the objective relationships set forth in the NYSE listing standards that prevent independence.

        In assessing the independence of Mr. Deninger, the Board considered Mr. Deninger's position as a senior managing director at Evercore Partners Inc., or Evercore. In 2013 the Company entered into an agreement with Evercore pursuant to which Evercore agreed to provide financial advisory services to the Company, as further described under the "Certain Relationships and Related Transactions" section of this Proxy Statement. In 2015 the Company paid the final $250,000 of fees associated with the agreement with Evercore. The agreement with Evercore has terminated in accordance with its terms. The Board determined that, because Mr. Deninger agreed to waive any direct fees he may receive in connection with the Evercore engagement and did not work on the engagement on behalf of Evercore, this relationship would not interfere with Mr. Deninger's ability to exercise independence from the Company.

The Board has determined that all of our non-management directors qualify as independent under NYSE rules. One of our directors, Mr. Meaney, is a management employee involved in our day-to-day activities and is not considered to be an independent director.

        Attendance.    During the fiscal year ended December 31, 2015,2016, the Board held 1310 meetings. Each incumbent director, except for Mr. Chatfield and Ms. Murdock, attended at least 75% of the aggregate number of meetings of the Board and all committees thereof on which such director served that were held during the period for which such director served.fiscal year ended December 31, 2016. Mr. Chatfield and Ms. Murdock are expected to joinjoined the Board on May 2, 2016 and did not attend any Board and committee meetings duringin connection with our acquisition of Recall. During the fiscal year ended December 31, 2015. All2016, Mr. Chatfield attended six and seven Board and committee meetings, respectively, and Ms. Murdock attended six and nine Board and committee meetings, respectively. Ten of our twelve directors standing for re-election at the time attended our 20152016 Annual Meeting of Stockholders.Stockholders attended such meeting. All directors standing for re-election at our Annual Meeting are expected to attend the Annual Meeting, either in person or by teleconference. Our policy with respect to directors' attendance at our annual meetings of stockholders can be found in our Corporate Governance Guidelines, the full text of which appears under the heading "Company/Investors/Corporate Governance" on our website at www.ironmountain.com.

Board Leadership Structure

        The Board does not have a formal policy as toon whether the roles of Chairman and CEO should be combined or separated. The Board believes that Iron Mountain stockholders are best served by the Board having flexibility to consider the relevant facts and circumstances and determine, at the time of the Chairman's election, the best leadership structure for the Company rather than by adhering to a formal standing policy on the subject.

        As a result ofIn connection with the Board's ongoing review of its leadership structure, the Board has determined that the position of Chairman should be held by a non-employeenon employee of the Company. The Board believes that the current leadership structure, which separates the roles of CEO and Independent Chairman, fosters effective governance and oversight of the Company. The Independent Chairman controls the Board meeting agendas, which ensures that topics deemed important by the independent directors are included in Board discussions and best enables the Board to express its views on our management, strategy and execution. The Independent Chairman is responsible for advising the CEO and presiding over meetings of the Board, presiding over all executive sessions of non-management directors, consulting with the CEO on Board meeting agendas and acting as a liaison between management and non-management directors. The CEO is responsible for setting the Company's strategy and leading the organization's day-to-dayday to day performance. We believe this governance structure promotes balance between the authority of those who oversee our business and those who manage it on a day-to-dayday to day basis.

        The Board convenes in non-management executive session before the conclusion of each in-person Board meeting, and an executive session is offered in all telephonic Board meetings.

Committees

        The Board has the following standing committees: Audit Committee, Compensation Committee, Nominating and Governance Committee, Finance Committee and Risk and Safety Committee. The Board has adopted a charter for each of its standing committees, and each such charter is available on our website at www.ironmountain.com under the heading "Company/Investors/Corporate Governance." During the fiscal year ended December 31, 2015,2016, the Audit Committee held six meetings, the Compensation Committee held sixeight meetings, the Nominating and Governance Committee held five meetings, the Finance Committee held ninesix meetings and the Risk and Safety Committee held sixfive meetings.

        The Nominating and Governance Committee annually reviews the composition of the Board committees and considers whether to recommend committee membership changes to the Board. In 2015As part of this process in 2016, the NominatingBoard added new directors to committees and Governance Committee, in an effort to promote continuity, did not recommend anymade other changes. Each committee membership changes.also maintained several of its existing members for continuity.

        Membership on each committee as of April 15, 20166, 2017 is set forth in the chart below.

Committee Membership

Upon the consummation of the Company's acquisition of Recall, each of Mr. Chatfield's appointment to the Board and Ms. Murdock's appointment to the Board will become effective. Mr. Chatfield is expected to join the Audit Committee and the Risk and Safety Committee, and Ms. Murdock is expected to join the Compensation Committee and the Finance Committee.

        Audit Committee.    Each member of the Audit Committee is independent as defined by the rules of the SEC, the NYSE listing standards and the Audit Committee Charter. In addition, the Board has determined that each member of the Audit Committee is an audit committee financial expert as defined by the rules of the SEC and is financially literate as defined by the NYSE listing standards. The Audit Committee: (1) assists the Board in oversight of the integrity of the Company's financial statements; (2) assists the Board in oversight of the Company's compliance with legal and regulatory requirements; (3) assists the Board in oversight of the independent registered public accounting firm's retention, qualifications and independence; (4) assists the Board in oversight of the performance of the Company's internal audit function and independent auditors; (5) prepares an Audit Committee report as required by the SEC to be included in the annual Proxy Statement; (6) performs such other duties as the Board may assign to the Audit Committee from time to time, such as approving transactions subject to our Related Person Transaction Policies and Procedures described on page 7390 of this Proxy Statement; and (7) takes other actions to meet its responsibilities as set forth in its written charter. The Audit Committee is also responsible for establishing procedures for the receipt, retention and treatment of complaints regarding accounting, internal accounting controls and auditing matters, including procedures for the confidential and anonymous submission by employees of the Company of any concerns regarding accounting or auditing matters they think may be questionable. Information about these procedures can be found on our website, www.ironmountain.com, under the heading "Company/Investors/Corporate Governance."

        Compensation Committee.    Each member of the Compensation Committee qualifies as independent under the NYSE listing standards. The Compensation Committee: (1) reviews, approves and recommends to the independent members of the Board the base salary, equity-based incentives and the payment of short-term incentive compensation for the CEO; (2) approves all long-term equity incentives to our employees, including Messrs. Day, Duale, Meaney and Keddy and Ms. Evens, or, collectively, the Named Executive Officers under the 2014 Stock and Cash Incentive Plan, or the 2014 Plan; (3) reviews and approves the annual cash compensation for Named Executive Officers (other

than the CEO) based on recommendations from the CEO and reports to the Board on such decisions; (4) reviews the Company's cash and stock-based incentive compensation plans to assess their effectiveness in meeting the Company's goals and objectives and exercises all of the authority of the Board with respect to the administration of such plans; (5) annually reviews and discusses with management a draft of the Company's Compensation Discussion and Analysis to be included in the Company's Annual Report on

Form 10-K and annual proxy statement; (6) annually prepares and publishes an annual report of the Compensation Committee for inclusion in the Company's Annual Report on Form 10-K and annual proxy statement; (7) reviews and discusses at least on an annual basis the risks arising from the Company's compensation policies for its employees; and (8) takes other actions to meet its responsibilities as set forth in its written charter.

        The Board has delegated final authority for compensation decisions for the Named Executive Officers, other than our CEO, to the Compensation Committee. The Compensation Committee has the authority to delegate any of its responsibilities to a sub-committee composed of members of the Compensation Committee, but it has not done so to date.

        For a discussion concerning the process and procedures for determining executive compensation and the role of executive officers and compensation consultants in determining or recommending the amount or form of compensation, see the "Compensation Discussion and Analysis" section in this Proxy Statement.

        Nominating and Governance Committee.    Each member of the Nominating and Governance Committee qualifies as independent under the NYSE listing standards. The Nominating and Governance Committee: (1) recommends the composition of the Board; (2) identifies and recommends candidates for nomination to the Board; (3) recommends to the Board structures and statements of the duties and responsibilities of each committee of the Board; (4) develops and recommends to the Board and implements corporate governance guidelines applicable to the Company; (5) assists the Board in annually reviewing management succession; (6) develops and monitors an annual process to assess the effectiveness of the Board and implements and oversees an annual review of the performance of the Board (including evaluations of individual Board members) and each of the Board's standing committees; (7) develops and proposes, for approval by the Board, compensation policies for the Company's non-employee directors; (8) annually reviews contributions to candidates made by the Iron Mountain Incorporated Political Action Committee, or IMPAC, and determines the composition of the IMPAC board; and (9) takes other actions to meet its responsibilities as set forth in its written charter.

        Finance Committee.    Although the NYSE listing standards do not require members of the Finance Committee to be independent, all members of the Finance Committee qualify as independent under the NYSE listing standards and the Board's assessment of any material relationships with the Company. The Finance Committee: (1) reviews the Company's capital structure and financial strategies; (2) reviews the Company's material capital allocation decisions, strategic investments and dispositions and other opportunities for maximizing stockholder value; (3) considers and reviews the Company's dividend and share repurchase policies and programs and other strategies to return capital to stockholders; (4) reviews the Company's derivatives and hedging policies and strategies; (5) reviews the Company's investment policies and practices; (6) reviews the Company's credit ratings and strategy, (7) periodically reviews the Company's investor relations strategy, (8) furnishes periodic reports to the Board concerning the Finance Committee's work; and (9) performs such other duties as the Board may assign to the committee from time to time.

        Risk and Safety Committee.    The Risk and Safety Committee (1) reviews and monitors material safety, security, business continuity, information security and risk management strategies and systems; (2) reviews and monitors material safety, security, business continuity, information security and risk management policies and processes implemented, established and reported on by the Company's

management; (3) monitors the Company's insurance programs; and (4) takes other actions to meet its responsibilities as set forth in its written charter.

Board and Committee Evaluations

        The Nominating and Governance Committee oversees the Board and committee evaluation process. Generally, including in 2015, the Board and each committee conduct self-evaluationsself evaluations by means of written questionnaires completed by each director and committee member. The anonymous responses are summarized and provided to the Board and each committee at their subsequent meetings in order to facilitate an examination and discussion by the Board and each committee of the effectiveness of the Board, committees, individual directors, Board and committee structure and dynamics, and areas for possible improvement. The Nominating and Governance Committee establishes the board and committee evaluation process each year and may determine to use an independent third party evaluation process from time to time in the future.

Risk Oversight

        The Board is responsible for oversight of the Company's management of enterprise risks. Iron Mountain senior management is responsible for the Company's risk management process and the day-to-dayday to day supervision and mitigation of enterprise risks. The Board receives regular reports on areas of material Company risk, including strategic, operational, financial, legal and regulatory risks. The Board, or the committee of the Board assigned responsibility for a specific area of risk, receives reports from the Company executive accountable for understanding and mitigating the identified risk. When a committee of the Board receives a risk report, the chairman of such committee provides a summary of the discussion to the Board during the next regularly scheduled Board meeting. This practice allows the Board and each of its committees to remain coordinated in their oversight of enterprise risk. The Risk and Safety Committee provides additional support to the Board in ensuring that the Company's enterprise risk management program is established appropriatelyappropriate and operating effectively.

Political Expenditures

        Our Global Political Contribution Policy, together with our Code of Ethics and Business Conduct, guide our approach to ethical business behavior and corporate political contributions. Our Global Political Contribution Policy provides that Iron Mountain does not make political contributions in any form or amount from corporate funds or resources, even when permitted by applicable law. This means corporate funds are not used in support of or opposition to political candidates, political parties, political committees and other political entities organized and operating for political candidates. In addition, corporate funds are not used for "electioneering" communications.

        The Company administers IMPAC, which is a non-partisannon partisan political action committee supporting congressional candidates at the federal level only. IMPAC allows eligible employees to pool their resources to support candidates who understand the issues important to the Company's business and its employees. Participation in IMPAC is strictly voluntary. Except for administrative expenses, IMPAC is funded solely by the Company's employees and directors and is not supported by funds from the Company. IMPAC complies with federal election laws and all other applicable laws and reports regularly to the Federal ElectionsElection Commission. In addition, IMPAC is governed by a set of bylaws and supervised by a board of directors composed of senior managers from different areas of the Company.

        The Company is a member of a number of trade associations that participate in public relations activities such as education and conferences, but not for the purpose of making political contributions. Our Code of Ethics and Business Conduct and our Global Political Contribution Policy are available on our website under the heading "Company/"About Us/Investors/Corporate Governance."

Stockholder Communications to Board of Directors

        The Board believes it is important to engage effectively with stockholders. To facilitate this engagement, in February 2016, the Board adopted a written Shareholder Engagement and

Communication Policy, or the Shareholder Engagement Policy, which outlines the procedures for the Board's engagement and communication with the Company's stockholders. The Shareholder Engagement Policy is overseen by the Nominating and Governance Committee. Under the Shareholder Engagement Policy, any stockholder, CDI holder, security holder or other interested party who desires to communicate with the Board, any individual director, including the Independent Chairman, or the independent or non-management directors as a group, may do so by regular mail or email directed to the Secretary of the Company. Communications to the Board should be mailed to Corporate Secretary, Iron Mountain Incorporated, One Federal Street, Boston, Massachusetts 02110; the Secretary's email address is corporatesecretary@ironmountain.com. Upon receiving such mail or email, the Secretary will assess the appropriate director or directors to receive the message and will forward the mail or email to such director or directors without editing or altering it.

Selection of Board of Directors Nominees

        The Board is responsible for developing and approving criteria, in addition to those set forth in our Corporate Governance Guidelines, for candidates for Board membership. The Nominating and Governance Committee is responsible for seeking candidates to become Board members, consistent with the criteria set forth in the Corporate Governance Guidelines and approved by the Board, and for recommending candidates to the entire Board for selection by the Board for nomination to fill vacancies on the Board or expiring terms of directors at each annual meeting of stockholders. The Board as a whole is responsible for nominating individuals for election to the Board by the stockholders and for filling vacancies on the Board that may occur between annual meetings of the stockholders.

        Nominees for director will be selected on the basis of their integrity, experience, achievements, judgment, intelligence, personal character, ability to make independent analytical inquiries, willingness to devote adequate time to Board duties and likelihood that they will be able to serve on the Board for a sustained period. In connection with the selection of nominees for director, the Board's policy is to give due consideration to the Board's overall balance of diversity of perspectives, backgrounds and experiences. To implement and review the effectiveness of our diversity policy, the Nominating and Governance Committee reviews the appropriate skills and characteristics of members of the Board in the context of the then current composition of the Board. It is the practice of the Nominating and Governance Committee to then consider these factors when screening and evaluating candidates for nomination or re-election to the Board. The Board will not nominate for election as director any candidate who has not agreed to tender, promptly following the annual meeting at which he or she is elected as director, an irrevocable resignation that will be effective upon (1) the failure to receive the required number of votes for re-election at the next annual meeting of stockholders at which he or she faces re-election, and (2) acceptance of such resignation by the Board.

        The Nominating and Governance Committee will consider, as part of the process for identifying individuals who might be candidates, individuals who are properly recommended by stockholders for nomination by the Board at a meeting of stockholders at which directors are to be elected. To be proper, a recommendation for a nominee for director with respect to a meeting of stockholders must comply with applicable law, the Company's Bylaws and the Company's Corporate Governance Guidelines. The Nominating and Governance Committee will consider any suggestions offered by other directors or stockholders with respect to potential directors, and there will be no difference in the manner in which potential nominees are evaluated. However, the Nominating and Governance Committee and the Board are not required to enlarge the size of the Board in order to nominate an otherwise fully qualified candidate proposed by a stockholder. A stockholder wishing to nominate a

director directly must comply with the procedures described in the Company's Bylaws and this Proxy Statement.

        In 20152016 the Nominating and Governance Committee did not retain the services of, and did not pay a fee to, any third party to identify or assist in identifying or evaluating potential nominees to our Board.

Nominations and Proposals of Stockholders

        A stockholder who, in accordance with Rule 14a-8, or Rule 14a-8, under the Securities Exchange Act of 1934, as amended, or the Exchange Act, wants to present a proposal for inclusion in the Company's 20172018 Proxy Statement and proxy card relating to the 20172018 Annual Meeting of Stockholders must submit the proposal by December 28, 2016.10, 2017. In order for the proposal to be included in the Proxy Statement, the stockholder submitting the proposal must meet certain eligibility standards and comply with certain regulations established by the SEC.

        Stockholders who wish to present a business proposal or nominate persons for election as directors at the Company's 20172018 Annual Meeting of Stockholders must provide a notice of the business proposal or nomination in accordance with Section 2.4 of our Bylaws, in the case of business proposals, or Section 3.2 of our Bylaws, in the case of director nominations. In order to be properly brought before the 20172018 Annual Meeting of Stockholders, Sections 2.4 and 3.2 of our Bylaws require that a notice of the business proposal the stockholder wishes to present (other than a matter brought pursuant to Rule 14a-8), or the person or persons the stockholder wishes to nominate as a director, must be received at our principal executive office not less than 90 days, and not more than 120 days, prior to the first anniversary of the Company's prior year's annual meeting. Therefore, any notice intended to be given by a stockholder with respect to the Company's 20172018 Annual Meeting of Stockholders pursuant to our Bylaws must be received at our principal executive office no earlier than February 17, 2017January 25, 2018 and no later than March 19, 2017.February 24, 2018. However, if the date of our 20172018 Annual Meeting of Stockholders occurs more than 30 days before or 30 days after June 17, 2017,May 24, 2018, the anniversary of the 20162017 Annual Meeting of Stockholders, a stockholder notice will be timely if it is received at our principal executive office by the later of (1) the 120^th day prior to such annual meeting or (2) the close of business on the tenth day following the day on which public disclosure of the date of the meeting was made. To be in proper form, a stockholder's notice must include the specified information concerning the stockholder and the business proposal or nominee, as described in Sections 2.4, 3.2 and 3.3 of our Bylaws.

        All proposals must be mailed to the Company's principal executive office, at the address stated herein, and should be directed to the attention of the Secretary of the Company.

Code of Ethics

        Our Code of Ethics and Business Conduct applies to each of the Company's employees, including officers, and directors. Our Code of Ethics and Business Conduct is posted on our website, www.ironmountain.com, under the heading "Company/"About Us/Investors/Corporate Governance." A printed copy of our Code of Ethics and Business Conduct is also available free of charge to any stockholder who requests a copy. We intend to disclose any amendment to, or waiver from, a provision of our Code of Ethics and Business Conduct applicable to our CEO, chief financial officer or principal accounting officer or controller by posting such information on our website. Any waivers applicable to any other executive officers will also be promptly disclosed to stockholders on our website.

ITEMPROPOSAL 2

AMENDMENT TO THE IRON MOUNTAIN INCORPORATED
2014 STOCK AND CASH INCENTIVE PLAN

        The Board has unanimously approved, and unanimously recommends that the stockholders of the Company approve, an amendment, attached as Appendix A, to the 2014 Plan to increase the number of shares of Common Stock authorized for issuance under the 2014 Plan by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value as of the date such award is granted. Fair Market Value, as used in this Proposal 2, means the "fair market value" as defined in the 2014 Plan.

        The Board believes that equity interests are a significant factor in the Company's ability to attract, retain and motivate key employees, directors and other service providers (generally, and in connection with acquisitions) that are critical to the Company's long-term success and that an increase in the number of shares available for issuance under the 2014 Plan is necessary in order to provide those persons with incentives to serve the Company.

        In approving the increase in the number of shares reserved for issuance under the 2014 Plan, the Board considered the following factors:

        Equity Run Rate.    As of March 27, 2017, only 2,994,785 total shares remained available for grant under the Company's equity plans, including 2,560,859 remaining available under the 2014 Plan and 433,926 remaining available under the Iron Mountain Incorporated 2002 Stock Incentive Plan. The Board currently believes that the proposed increase of 5,000,000 shares under the 2014 Plan should result in an adequate number of shares of Common Stock for future awards for approximately four years, although this forecast includes several assumptions and there are a number of factors that could impact the Company's future equity share usage. Among the factors that will impact the Company's share usage are: changes in market grant values; changes in the number of recipients; changes in the Company's stock price; payout levels of performance-based awards; changes in the structure of the Company's long-term incentive programs; and forfeitures of outstanding awards.

        Overhang.    If stockholders approve the increase in the reserve under the 2014 Plan, the total shares available for grant under all of the Company's equity plans would be 7,994,785 and would represent approximately 3.03% of 264,098,277 shares of Common Stock outstanding as of March 27, 2017.

        As of March 27, 2017, the Company had approximately 1,841,656 full value awards outstanding under all of its equity plans. In addition, as of March 27, 2017, the Company had approximately 4,317,577 stock options outstanding under all of its equity plans, which stock options had a weighted average exercise price of $33.28 and a weighted average remaining term of 7.57 years. If stockholders approve the amendment to the 2014 Plan, as of March 27, 2017, the potential overhang⁽¹⁾ from all stock awards granted and available to employees and directors would increase from 3.35% to 5.09%.

        As a result of increasing the number of shares, it is also possible to extend the termination date of the 2014 Plan, which the Board believes is an appropriate action.

⁽¹⁾

Overhang is calculated by dividing (1) the sum of (i) the number of shares of Common Stock subject to equity awards outstanding as of March 27, 2017 and (ii) the number of shares of Common Stock available for future grants, by (2) the sum of (x) number of shares of Common Stock outstanding as of March 27, 2017 and (y) equity awards outstanding and available for grant.

        In addition, the amendment to the 2014 Plan will provide that the aggregate economic value of all equity-based and equity-related awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each award, by using the Fair Market Value as of the date such award is granted. This limit shall not apply to any award or shares granted pursuant to a non-employee director's election to receive an award or shares in lieu of cash retainers or other fees (to the extent such award or shares have a fair value equal to the value of such cash retainers or other fees) or the investment of deferred cash retainers or other fees in phantom stock pursuant to the Iron Mountain Incorporated Directors Deferred Compensation Plan, or the DDCP. The Board believes that providing for a limit on the aggregate economic value of all awards granted under the 2014 Plan to each director who is not an employee of the Company is consistent with the principles of good corporate governance and will promote the interests of stockholders and is advisable in light of recent increased focus on non-employee director compensation.

        The closing price of the Company's Common Stock on March 27, 2017 was $34.58.

Summary of the 2014 Plan

        The following summary of the material features of the 2014 Plan is qualified in its entirety by reference to the complete text of the 2014 Plan, which is filed as an appendix to the Company's Proxy Statements on Schedule 14A filed on December 23, 2014.

        The 2014 Plan permits the issuance of equity-based awards, including incentive stock options, or ISOs, nonqualified stock options, or NSOs, grants of Common Stock, whether or not subject to restrictions, stock appreciation rights, or SARs, restricted stock units, or RSUs, and performance units, or PUs, that vest based on certain performance criteria, and cash-based awards that may be earned based on certain performance criteria, or, collectively, Awards. The 2014 Plan initially reserved 7,750,000 shares of Common Stock. If stockholders approve the proposed amendment to the 2014 Plan, the total amount of Common Stock authorized for issuance under the 2014 Plan will be 12,750,000.

        Effective Date and Duration.    The 2014 Plan became effective on January 20, 2015. The 2014 Plan provides for termination on January 20, 2025 or May 24, 2027 if the proposed amendment is adopted, unless earlier terminated by the Board. Termination of the 2014 Plan will not affect Awards made prior to termination, but no new Awards will be made after the 2014 Plan terminates.

        Purpose and Eligibility.    The purpose of the 2014 Plan is to advance the interests of our stockholders by enhancing our ability to attract, retain and motivate persons who are expected to make important contributions to us and our affiliates, and to provide those persons with equity ownership opportunities and performance-based equity and cash compensation. For this purpose, any present or future parent or subsidiary corporation, and any other present or future business venture in which we have a controlling interest, may be treated as an affiliate of ours.

        The persons eligible to receive Awards are our and our affiliates' employees, officers, directors, consultants and advisors and those of our affiliates. The recipient of an Award under the 2014 Plan is referred to below as a Participant. At this time, we consider approximately 1,300 persons eligible to receive Awards pursuant to the 2014 Plan.

        Administration.    Although our Board has the authority to administer the 2014 Plan, it has generally delegated this authority to the Compensation Committee, which administers all of our equity-based compensation plans. Each member of the Compensation Committee is a "non-employee director" within the meaning of Rule 16b-3 promulgated under the Exchange Act, an "outside director" within the meaning of Section 162(m) of the Code and qualifies as independent under NYSE listing standards.

        Subject to the terms of the 2014 Plan, the Compensation Committee has the authority to: (1) select or approve Award recipients; (2) determine the terms and conditions of Awards, including the price to be paid for any Common Stock; and (3) interpret the 2014 Plan and prescribe rules and regulations for its administration.

        Awards, at the discretion of the Compensation Committee, may be transferable to members of a Participant's immediate family or to a family partnership or trust for the benefit of a Participant's immediate family.

        Shares Subject to the 2014 Plan.    The total number of shares of our Common Stock that may be subject to Awards under the 2014 Plan may not exceed 7,750,000 shares, or 12,750,000 shares if the proposed amendment is approved. The shares may be authorized but unissued shares or treasury shares. The total amount of Common Stock that may be granted under the 2014 Plan to any single person in any year may not exceed in the aggregate 1,250,000 shares; provided, however, that if the proposed amendment is adopted, then the aggregate economic value of all equity-based and equity-related Awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each Award, by using the Fair Market Value as of the date such Award is granted. In the event a cash-based Award under the 2014 Plan is made, such Award shall not exceed $7,500,000 in any year to any single person. Both the limit on the maximum number of shares and the limit on the maximum cash-based award that may be granted to a single person are designed to help qualify Awards under the 2014 Plan for the performance-based compensation exemption to the deduction limit applicable under Section 162(m) of the Code.

        To the extent that an option or other form of Award lapses or is forfeited, the shares subject to the Award will again become available for grant under the terms of the 2014 Plan.

        As of March 27, 2017, 4,586,210 equity-based Awards were outstanding, consisting primarily of stock options, target PUs and RSUs.

        Stock Options.    The Compensation Committee may grant ISOs and NSOs under the 2014 Plan. The Compensation Committee determines the number of shares of Common Stock subject to each option, its exercise price, its duration and the manner and time of exercise; provided, however, that no option may be issued under the 2014 Plan with an exercise price that is less than the Fair Market Value of our Common Stock as of the date the option is granted, and no option will have a duration that exceeds ten years. ISOs may be issued only to employees of the Company or a corporate subsidiary thereof and, in the case of a more than ten percent stockholder, must have an exercise price that is at least 110% of the Fair Market Value of our Common Stock as of the date the option is granted, and may not have a duration of more than five years.

        The Compensation Committee, in its discretion, may provide that any option is subject to vesting limitations that make it exercisable during its entire duration or during any lesser period of time.

        The exercise price of an option may be paid in cash, by delivery of a recourse promissory note secured by the Common Stock acquired upon exercise of the option (except that such a loan would not be available to any of our executive officers or directors), by means of a "cashless exercise" procedure in which a broker transmits to us the exercise price in cash, either as a margin loan or against the Participant's notice of exercise and confirmation by us that we will issue and deliver to the broker stock certificates for that number of shares of Common Stock having an aggregate Fair Market Value equal to the exercise price, or agrees to pay the exercise price to us in cash upon our receipt of stock certificates, by delivery of shares of Common Stock owned by the Participant, by a "net exercise" in the case of an NSO or by any combination of the methods listed.

        Except in connection with a corporate transaction involving the Company, the terms of an option may not be amended to reduce the exercise price (or cancel the option for cash, other Awards or other

options with an exercise price less than the exercise price of the existing option) without stockholder approval.

        Stock Appreciation Rights.    The Compensation Committee may also grant SARs to Participants on such terms and conditions as it may determine. SARs may be granted separately or in connection with an option. No SAR may be issued under the 2014 Plan with an exercise price that is less than the Fair Market Value of our Common Stock as of the date the SAR is granted, and no SAR will have a duration that exceeds ten years. Upon the exercise of an SAR, the Participant is entitled to receive payment equal to the excess of the Fair Market Value, on the date of exercise, of the number of shares of Common Stock for which the SAR is exercised over the exercise price for the Common Stock under a related option or, if there is not a related option, over an amount per share stated in the agreement setting forth the terms and conditions of the SAR.

        Payment to the Participant may be made in cash or other property, including Common Stock, in accordance with the provisions of the SAR agreement.

        Except in connection with a corporate transaction involving the Company, the terms of an SAR may not be amended to reduce the exercise price (or cancel an SAR for cash, other Awards or other SARs with an exercise price less than the exercise price of the existing SAR) without stockholder approval.

        Stock Grants.    The Compensation Committee may make an Award in the form of one or more of the following forms of Stock Grant. Stock Grants (including RSUs and PUs at settlement) generally will provide the Participant with all of the rights of a stockholder of ours, including the right to vote and to receive payment of dividends.

        Stock Grant without Restriction.    The Compensation Committee may make a Stock Grant without any restrictions.

        Restricted Stock and Restricted Stock Units.    The Compensation Committee may issue shares of Common Stock to a Participant with restrictions determined by the Compensation Committee in its discretion. Restrictions could include conditions that require the Participant to forfeit the shares in the event that the Participant ceases to provide services to us or any of our affiliates thereof before a stated time.

        RSUs are similar to restricted stock except that no shares are actually issued to the Participant on the RSU grant date. Rather, and provided all applicable restrictions are satisfied, shares of Common Stock are generally delivered at settlement of the Award. The period of restriction, the number of shares of restricted stock or the number of RSUs granted, the purchase price, if any, and such other conditions and/or restrictions as the Compensation Committee may establish will be set forth in an Award agreement.

        Participants holding RSUs will not have voting rights or other rights as a stockholder until any shares related to the RSU are issued. After all conditions and restrictions applicable to restricted shares and/or RSUs have been satisfied or have lapsed, shares of restricted stock will become freely transferable and RSUs may be settled in cash, in shares of our Common Stock or in some combination of cash and shares of our Common Stock, as determined by the Compensation Committee and stated in the Award agreement.

        Performance Shares and Performance Units.    With respect to an Award of performance shares and/or PUs, the Compensation Committee will establish performance periods and performance goals. The extent to which a Participant achieves his or her performance goals during the applicable performance period will determine the value and/or the number of performance shares and/or PUs earned by such Participant. Payment of earned performance shares and/or PUs will be in cash, shares

of our Common Stock or some combination of cash and shares of our Common Stock, as determined by the Compensation Committee and stated in the Award agreement.

        Dividends.    Participants holding restricted stock and performance shares will be entitled to receive dividends on our shares, provided that in the discretion of the Compensation Committee Participants will not be entitled to dividends with respect to unvested restricted stock and performance shares until the stock or shares vest, respectively. Dividend equivalent units may, but are not required to, be issued with respect to RSUs or PUs and may be paid in cash, additional shares of our Common Stock or a combination on the date the shares are delivered, all as determined by the Compensation Committee and stated in the Award agreement.

        Cash-Based Awards.    The Compensation Committee may make a cash-based Award in an amount and upon such terms as the Compensation Committee may determine, based on the achievement of performance goals established by the Compensation Committee.

        Performance Goals.    If the Compensation Committee makes an Award intended to qualify as "performance-based compensation" under Section 162(m) of the Code (including a PU or a cash-based Award), the performance goals selected by the Compensation Committee must be based on the achievement of specified levels of one, or any combination, of the following business criteria, measured in the aggregate or on a per share basis (if appropriate): EBITDA (earnings before interest, taxes, depreciation and amortization); OIBDA (operating income before depreciation and amortization); adjusted OIBDA or Contribution (as defined in the 2014 Plan); gross revenues; storage rental revenue; growth rate; capital spending; capital efficiency; maintenance capital spending; free cash flow; funds from operations (as defined by the National Association of Real Estate Investment Trusts); funds from operations (normalized); adjusted funds from operations; building utilization; racking utilization; dividends; same store sales; same store net operating income; operating income (before or after taxes); net operating income; attaining budget; return on total or incremental invested capital; gross profit or margin; operating profit or margin; net earnings (before or after taxes); earnings per share; adjusted earnings per share; net income; share price (including but not limited to growth measures and total stockholder return); return on assets, return on equity, return on sales or return on revenue; other cash flow measures (including operating cash flow, cash flow return on equity, cash flow return on investment and free cash flow before acquisitions and discretionary investments); productivity ratios or metrics; market share; customer satisfaction; working capital targets; storage volume; organizational or transformational metrics; and achievement of stated corporate goals including, but not limited to acquisitions or dispositions, alliances, joint ventures, international development, and internal expansion. The Compensation Committee has the discretion to choose other performance goals with regard to any particular Award, but that Award may not qualify as "performance-based compensation" under Section 162(m) of the Code.

        Any such criteria, whether alone or in combination, may be applied on the basis of our and/or our affiliates as a whole or on any business unit or subset of us and/or an affiliate of ours and may be measured directly, as a growth rate or by comparing the result to the performance of a group of competitor companies, a published or special index determined by the Compensation Committee or other benchmarks determined by the Compensation Committee. The objectives shall be further adjusted by the Compensation Committee as necessary to eliminate the effect on the stated performance goals of unplanned acquisitions or dispositions, changes in foreign exchange rates, discrete tax items identified by the Compensation Committee, changes in accounting standards, variances to planned annual incentive compensation expense and expenses associated with unusual or extraordinary items that could not be reasonably anticipated, as long as those items or changes are material to the performance measure.

        For purposes of satisfying the performance-based exception under Section 162(m) of the Code, the Compensation Committee has the discretion to reduce, but not increase, a performance-based Award

(but the Compensation Committee can provide in a grant for an additional Award in the event the relevant performance goals are exceeded).

        After the close of the applicable performance period, which may consist of more than one year, and generally before the close of the next year's first quarter, the Compensation Committee will determine the extent to which the performance goals were satisfied and make a final determination with respect to an Award.

        In the event that applicable tax laws change to permit Compensation Committee discretion to alter the performance goals without obtaining stockholder approval, the Compensation Committee will have sole discretion to make any such alterations.

        Effect of Certain Corporate Transactions.    In the event of a stock split, reverse stock split, stock dividend, recapitalization, combination of shares, reclassification of shares, spin-off or other similar change in capitalization or event, or any dividend or distribution on our Common Stock other than an ordinary cash dividend, the Compensation Committee shall make equitable adjustments to Awards as it, in its sole discretion, deems appropriate. In the case of (1) a merger or consolidation of the Company with or into another entity pursuant to which all of our Common Stock is cancelled or converted into or exchanged for the right to receive cash, securities or other property, (2) any transfer or disposition of all of our Common Stock for cash, securities or other property pursuant to a share exchange or other transaction, (3) the sale or other disposition of all or substantially all of the Company's assets or (4) any liquidation or dissolution of the Company, the Compensation Committee may take any of a number of actions including providing for the assumption of Awards, the termination of Awards (with advance notice permitting exercise), Awards to become exercisable at or prior to the event, the liquidation of Awards or any combination of the foregoing.

        The 2014 Plan also provides that any unvested Awards will generally vest immediately should a Participant be terminated by us or our successor (or should the Participant terminate for "good reason") in connection with a "vesting change in control" within 14 days prior or 12 months after the vesting change in control.

        A vesting change of control is generally defined to include, among other things: (1) a sale of us or substantially all of our assets; (2) the acquisition by a person or group of securities representing 50% or more of the voting power of the Company's securities entitled to vote in the election of directors; or (3) certain changes in the composition of our board of directors over a period of time that are not approved by our board of directors. "Good reason" for this purpose is generally defined to include: (i) a diminution in the total annual compensation or material diminution in benefits the Participant is eligible to receive; or (ii) a requirement by us that the Participant be based at an office that is greater than 50 miles from the location of the Participant's office immediately prior to the vesting change in control.

        Amendments to the 2014 Plan.    Our board of directors may amend, suspend or terminate the 2014 Plan in whole or in part at any time provided that stockholder approval shall be required to the extent necessary under Section 162(m) of the Code, under the rules applicable to ISOs or under NYSE or other applicable securities exchange rules.

        The Compensation Committee may, without stockholder approval, amend the 2014 Plan as necessary to enable Awards to qualify for favorable foreign tax, securities or other treatment in the case of a Participant who is subject to a jurisdiction outside the United States.

Tax Treatment

        The following description of the federal income tax consequences of Awards is general, does not purport to be complete and does not describe state, local or foreign tax consequences.

        Tax Treatment of Nonqualified Stock Options.    A Participant realizes no taxable income when an NSO is granted. Instead, the difference between the Fair Market Value of the Common Stock acquired pursuant to the exercise of the option and the exercise price paid is taxed as ordinary compensation income when the option is exercised. The difference is measured and taxed as of the date of exercise, if the Common Stock is not subject to a "substantial risk of forfeiture," or as of the date or dates on which the risk terminates in other cases. A Participant may elect to be taxed on the difference between the exercise price and the Fair Market Value of the Common Stock on the date of exercise, even though some or all of the Common Stock acquired is subject to a substantial risk of forfeiture. Once ordinary compensation income is recognized, gain on the subsequent sale of the Common Stock is taxed as short-term or long-term capital gain, depending on the holding period after exercise. We receive no tax deduction on the grant of a nonqualified stock option, but we are entitled to a tax deduction when a Participant recognizes ordinary compensation income on or after exercise of the option, in the same amount as the income recognized by the Participant.

        Tax Treatment of Incentive Stock Options.    Generally, a Participant incurs no federal income tax liability on either the grant or the exercise of an ISO, although a Participant will generally have taxable income for alternative minimum tax purposes at the time of exercise equal to the excess of the Fair Market Value of the Common Stock subject to the option over the exercise price. Provided that the Common Stock is held for at least one year after the date of exercise of the option and at least two years after its date of grant, any gain realized on a subsequent sale of the Common Stock will be taxed as long-term capital gain. If the Common Stock is disposed of within a shorter period of time, the Participant will recognize ordinary compensation income in an amount equal to the difference between the Fair Market Value of the stock on the date of exercise (or the sale price of the shares sold, if less) over the exercise price. We receive no tax deduction on the grant or exercise of an ISO, but we are entitled to a tax deduction if the Participant recognizes ordinary compensation income on account of a premature disposition of shares acquired on exercise of an ISO, in the same amount and at the same time as the Participant recognizes income.

        Tax Treatment of Stock Appreciation Rights.    A Participant realizes no income upon the grant of an SAR, but upon its exercise recognizes ordinary compensation income in an amount equal to the cash or cash equivalent received at that time. If the Participant receives Common Stock upon exercise of an SAR, he or she recognizes ordinary compensation income equal to the Fair Market Value of the Common Stock received (reduced, if applicable, by the base amount set forth in the related agreement), assuming the Common Stock is not subject to a substantial risk of forfeiture at exercise. We are entitled to a tax deduction in the amount of ordinary compensation income recognized.

        Tax Treatment of Stock Grants.    A person who receives an Award of Common Stock without any restrictions will recognize ordinary compensation income equal to the Fair Market Value of the Common Stock over the amount (if any) paid. If the Common Stock is subject to restrictions, the recipient generally will not recognize ordinary compensation income at the time the Award is received but will recognize ordinary compensation income when restrictions constituting a substantial risk of forfeiture lapse. The amount of that income will be equal to the excess of the aggregate Fair Market Value, as of the date the restrictions lapse, over the amount (if any) paid for the Common Stock. Alternatively, a Participant may elect to be taxed, pursuant to Section 83(b) of the Code, on the excess of the Fair Market Value of the Common Stock at the time of grant over the amount (if any) paid for the Common Stock, notwithstanding any restrictions. All such taxable amounts are deductible by us at the time and in the amount of the ordinary compensation income recognized by the Participant.

        A Participant who receives RSUs or PUs generally will not recognize ordinary compensation income at the time of grant. Rather, the Participant will generally recognize ordinary compensation income equal to the Fair Market Value of the Common Stock or cash received less the price paid, if any, at the time the RSU or PU settles shortly after vesting. When any Common Stock received is

subsequently sold, the Participant generally will recognize capital gain or loss equal to the difference between the amount realized upon the sale of the shares and his or her tax basis in the shares (generally, the Fair Market Value of the stock when acquired plus any amount paid). The capital gain or loss will be long-term if the stock was held for more than one year or short-term if held for a shorter period. The Company will be entitled to a tax deduction when the Participant recognizes ordinary compensation income.

        Dividends.    The full amount of dividends or other distributions of property made with respect to Stock Grants before the lapse of any applicable restrictions will constitute ordinary compensation income, and the Company is entitled to a deduction at the same time and in the same amount as the income is realized by the Participant (unless an election under Section 83(b) of the Internal Revenue Code has been made). Dividend equivalents on RSUs and PUs will be taxed as additional ordinary compensation income at settlement, and we will be entitled to a deduction at the same time and in the same amount.

        Section 162(m) of the Code.    Section 162(m) of the Code generally disallows an income tax deduction to public companies for compensation in excess of $1,000,000 paid in any year to the principal executive officer and the three other most highly compensated executive officers, but generally not including the principal financial officer, to the extent that this compensation is not "performance-based" within the meaning of Section 162(m) of the Code. Compensation in excess of the $1,000,000 limit may be deducted if, among other matters, amounts are paid pursuant to pre-established, objective performance goals determined by a committee consisting solely of two or more "outside directors" (within the meaning of Section 162(m) of the Code), the material terms of those goals are disclosed to and approved by stockholders and any payment is made only after a committee of outside directors certifies that the pre-established performance goals have been satisfied.

        Options and SARs issued under the 2014 Plan generally satisfy the performance-based compensation exception under regulations issued pursuant to Section 162(m) of the Code if the grants are made by the Compensation Committee (a committee presently consisting of "outside directors") and the amount of compensation a person can receive under the option or SAR is based solely on an increase in the value of the stock after grant.

        Other forms of equity and cash Awards under the 2014 Plan, including in particular performance shares, PUs and certain cash-based Awards, are eligible for the performance-based exception to the extent the Compensation Committee satisfies the applicable requirements such as using performance goals included in the 2014 Plan and taking certain actions on a timely basis. Nevertheless, the deductibility of compensation is but one of the critical factors in the design and implementation of any compensation arrangement, and the Compensation Committee and our Board reserve the right to pay nondeductible compensation when appropriate.

Award Information

        The benefits or amounts that may be received or allocated to any individual under the 2014 Plan are not determinable, other than amounts that may be received by each non-employee director under Iron Mountain's existing Compensation Plan for Non-Employee Directors, which provides for an annual stock grant of that number of whole shares of Iron Mountain Common Stock determined by dividing $135,000 by the stock's Fair Market Value on the date of grant, in addition to various cash retainers.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to approve the amendment to the 2014 Plan to increase the number of shares of Common Stock issuable thereunder by 5,000,000 from 7,750,000 to 12,750,000, to extend the termination date of

the 2014 Plan from January 20, 2025 to May 24, 2027 and to provide that the aggregate economic value of all equity-based and equity-related Awards granted under the 2014 Plan in any year to any director who is not an employee of the Company shall not exceed $500,000, determined, for each Award, by using the Fair Market Value as of the date such Award is granted.

        For the purpose of determining whether a majority of the votes have been cast in favor of the approval of the amendment to the 2014 Plan, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination. Additionally, NYSE rules require that at least a majority of the votes that all stockholders are entitled to cast at the Annual Meeting must vote on the proposed amendment, whether for or against. Because the NYSE requirement sets the higher standard, this item will not pass unless the number of votes meeting the NYSE voting requirements have been cast on this matter.

The Board recommends that you vote FOR the approval of the amendment to the 2014 Plan.

PROPOSAL 3

ADVISORY VOTE ON THE COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

        In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including this separate proposal subject to stockholder vote to approve, on a non-binding, advisory basis, the compensation of our Named Executive Officers listed in the "SummarySummary Compensation Table"Table appearing inon page 75 of this Proxy Statement, as disclosed in this Proxy Statement pursuant to Item 402 of Regulation S-K.

        Our executive compensation is designed to reward executive performance that contributes to our success while encouraging behavior that is in our and our stockholders' long-term best interests. We also seek to attract, motivate, reward and retain the senior management talent required to achieve our corporate objectives and increase stockholder value. At the core of our executive compensation programs is our "pay for performance" philosophy that links competitive levels of compensation to achievements of our overall strategy and business goals, as well as predetermined objectives. We believe our compensation program is strongly aligned with the interests of our stockholders and sound corporate governance principles. We urge you to read the "Compensation Discussion and Analysis" section of this Proxy Statement and compensation tables and narrative discussion in this Proxy Statement for additional details on our executive compensation, including our compensation philosophy and objectives and the compensation of our Named Executive Officers.

        The vote on this proposal is not intended to address any specific element of compensation; rather, the vote relates to the compensation of our Named Executive Officers, as described in this Proxy Statement in accordance with the compensation disclosure rules of the SEC. To the extent there is any significant vote against the compensation paid to the Named Executive Officers as disclosed in this Proxy Statement, the Compensation Committee will evaluate whether any actions are necessary to address the concerns of stockholders.

        Based on the above, we request that you indicate your support for our executive compensation philosophy and practices by voting to approve, on a non-binding, advisory basis, the following resolution:

        "RESOLVED, that the compensation paid to the Company's Named Executive Officers, as disclosed pursuant to Item 402 of Regulation S-K, including the Compensation Discussion and Analysis, compensation tables and narrative discussion in the Proxy Statement for the 20162017 Annual Meeting of Stockholders, is hereby APPROVED."

Required Vote

        The affirmative vote of a majority of the votes properly cast at the Annual Meeting is required to approve the compensation of our Named Executive Officers, as described in the "Compensation Discussion and Analysis" section of this Proxy Statement, the compensation tables and the other narrative compensation disclosures contained in this Proxy Statement. For the purpose of determining whether a majority of the votes has been cast in favor of the approval of this resolution, only those cast "For" or "Against" are included, and any abstentions or broker non-votes will not count in making that determination. The opportunity to vote on this resolution is required pursuant to Section 14A of the Exchange Act. However, as an advisory vote, the vote on this resolution is not binding upon the Company and serves only as a recommendation to ourthe Board. Nonetheless, the Compensation Committee, which is responsible for designing and administering our executive compensation programs, and the Board value the opinions expressed by stockholders and will consider the outcome of the vote when making future compensation decisions for our Named Executive Officers.

        Our current policy is to provide stockholders with an opportunity to approve the compensation paid to our Named Executive Officers each year at our annual meeting of stockholders. WeSubject to the approval of the advisory vote on proposal four below, we currently expect that the next such vote will occur at our 20172018 Annual Meeting of Stockholders.

        The Board recommends that you vote FOR the approval of the foregoing non-binding, advisory resolution approving the compensation of our Named Executive Officers.

ITEM 3PROPOSAL 4

ADVISORY VOTE ON THE FREQUENCY OF THE ADVISORY VOTE ON COMPENSATION OF OUR NAMED EXECUTIVE OFFICERS

        In accordance with the requirements of Section 14A of the Exchange Act and related rules of the SEC, we are including a separate proposal subject to stockholder vote to recommend, on a non-binding, advisory basis, whether the non-binding, advisory stockholder vote to approve the compensation of our Named Executive Officers (that is, a vote similar to the non-binding, advisory vote in proposal three above) should occur every one, two or three years.

        By voting with respect to this proposal, stockholders may indicate whether they would prefer that we conduct future advisory votes on our Named Executive Officer compensation once every one, two or three years. Stockholders also may, if they so wish, abstain from casting a vote on this proposal.

        The Board has considered the frequency of the advisory vote on the compensation of our Named Executive Officers that it should recommend. After considering the benefits and consequences of each alternative for the frequency of submitting the advisory vote on the compensation of our Named Executive Officers to stockholders, the Board recommends submitting the advisory vote on the compensation of our Named Executive Officers to our stockholders annually.

        We believe an annual advisory vote on the compensation of our Named Executive Officers will allow us to obtain information on stockholders' views of the compensation of our Named Executive Officers on a more consistent basis compared to longer intervals. In addition, we believe an annual advisory vote on the compensation of our Named Executive Officers will provide our Board with frequent input from stockholders on our compensation programs for our Named Executive Officers. Finally, we believe an annual advisory vote on the compensation of our Named Executive Officers aligns more closely with our objective to engage in regular dialogue with our stockholders on corporate governance matters, including our executive compensation philosophy, policies and programs.

        For the above reasons, the Board recommends that you vote to hold a non-binding, advisory vote on the compensation of our Named Executive Officers annually. Your vote, however, is not to approve or disapprove the Board's recommendation.

        When voting on this proposal, you have four choices: you may elect that we hold an advisory vote on the compensation of our Named Executive Officers every year, every two years or every three years, or you may abstain from voting. If you properly complete your proxy and fail to indicate your preference or abstention, your shares will be voted to select every one year as the frequency with which our stockholders will be asked to hold a non-binding, advisory vote on the compensation of our Named Executive Officers. If you properly complete your CDI voting instruction form and fail to indicate your preference or abstention, the shares represented by your CDIs will not be voted with respect to this proposal.

Required Vote

        The frequency that receives the highest number of votes will be considered the frequency recommended by stockholders to hold a non-binding, advisory vote on the compensation of our Named Executive Officers. The Compensation Committee will consider the outcome of the vote when determining how frequently to hold a vote on the compensation of our Named Executive Officers. However, as an advisory vote, the vote on this proposal four is not binding upon us and serves only as a recommendation to the Board, and the Board may decide that it is in the best interests of our stockholders and our company to hold an advisory vote on executive compensation more or less frequently than the alternative approved by our stockholders.

The Board recommends a vote to hold a non-binding, advisory vote on the compensation of our Named Executive Officers EVERY YEAR.

PROPOSAL 5

RATIFICATION OF THE SELECTION OF
INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        Subject to ratification by the stockholders, the Audit Committee has selected the firm of Deloitte & Touche LLP as the Company's independent registered public accounting firm for the current year.

        Representatives of Deloitte & Touche LLP are expected to be present at the Annual Meeting. They will have the opportunity to make a statement if they desire to do so and will be available to respond to appropriate questions from stockholders who are present at the Annual Meeting.

        The fees we paid to Deloitte & Touche LLP in 20152016 are shown in the table appearing on page 7591 of this Proxy Statement.

        If the stockholders do not ratify the selection of Deloitte & Touche LLP as the Company's independent registered public accounting firm, the selection of accountants will be reconsidered by the Audit Committee.

Required Vote

        The affirmative vote of holders of a majority of the votes properly cast at the Annual Meeting is required to ratify the selection of Deloitte & Touche LLP to serve as the Company's independent registered public accounting firm for the current fiscal year. For purposes of determining the number of votes cast, only those cast "For" or "Against" are included, and any abstentions will not count in making that determination.

        The Board recommends that you vote FOR the ratification of the selection of Deloitte & Touche LLP.

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

        The following table sets forth certain information known to the Company with respect to beneficial ownership of Common Stock by: (1) each director and nominee for director; (2) the Named Executive Officers; (3) all directors and executive officers of the Company as a group; and (4) each stockholder known by us to be the beneficial owner of more than 5% of the Common Stock. Such information is presented as of March 31, 2016,2017, except as otherwise noted.

Equity Compensation Plan InformationEQUITY COMPENSATION PLAN INFORMATION

        The following provides certain equity compensation plan information with respect to all of our equity compensation plans in effect as of December 31, 2015:2016:

EXECUTIVE COMPENSATION
COMPENSATION DISCUSSION AND ANALYSIS

Executive Summary

        The primary objectives of our compensation programs are to reward the achievement of both Company and individual goals and to align the interests of our executives with the creation of stockholder value. In keeping with these objectives, our compensation programs are designed to align with the objectives of our strategic plan developed by senior leadership, or the Strategic Plan, and reward teamwork and contribution to the successful achievement of our enterprise goals and financial objectives.

20152016 Developments

•

Reaffirmed our Strategic Plan, which is focused on three core pillars for growth—Developed Markets⁽¹⁾, Emerging Markets⁽²⁾ and Adjacent Businesses⁽³⁾; extended our financial outlook to 2020 at our Investor Day in October 2015; and embarked on a multi-year transformation program, orCompleted the Transformation Program, intended to improve operational efficiency and provide additional investment for growthacquisition of Recall



•

Exceeded 2016 expected synergies



•

Entered into agreement to acquire Recall, which isImplemented synergy actions during 2016 that, on a full year basis, represent more than 85% of the total expected to deliver meaningful synergies and earnings accretion once completedfor 2017



•

Achieved operational performance generally in line with expectations measured



•

Continued to execute the Strategic Plan, making demonstrable gains in constant currency; however, the strengtheningeach of the U.S. dollar negatively impacted our reported resultsthree core growth and value pillars: Developed Markets⁽²⁾, Emerging Markets⁽³⁾ and Adjacent Businesses⁽⁴⁾



•

The transformation initiative we began in 2015, or the Transformation Initiative, continued to produce benefits that allowed the Company to invest in Adjacent Businesses, innovation and dividend growth



•

Continued to deliver rewards through our pay-for-performance model that balances short-term operational performance and the creation of long-term stockholder value:



•

our executives were rewarded for 20152016 operational performance through our short-term incentive program



•

the value of our executives' long-term incentives, the largest portion of their compensation, declined significantly due to the declinebenefited from an increase in our share price during 2015 and the impact of the strengthening U.S. dollar on the performance2016, partially offset by underperformance of certain of our Performance Units, or PUs which are measured on a reported basis (i.e., includingdue to the impactcontinued strength of currency fluctuation)the U.S. dollar since 2014

Strategic PlanLeadership Transition

        During 2015, we continuedChief Financial Officer

        On June 13, 2016, the Company and Mr. Roderick Day mutually agreed that Mr. Day would step down as the Company's Executive Vice President and Chief Financial Officer effective August 4, 2016, due to make progress executing on the Strategic Plan, which includes (i) three core growth and value pillarspersonal reasons that drive our business strategydid not permit him to generate more income from developed markets and higher growth markets and businesses and (ii) enabling activities that are designedpermanently relocate his family to improve efficiency and leverage scale to support the investment and executionBoston, as originally anticipated. Mr. Day remained an employee of the threeCompany through October 14, 2016 to assist in the transition of his responsibilities. Under the terms of his separation agreement, Mr. Day is entitled to be paid the benefits under the Company's plans, including without limitation the Iron Mountain Companies Severance Plan and Severance Program No. 1, or the Severance Program, which are described under the "Termination and Change of Control Arrangements" section of this Proxy

⁽¹⁾⁽²⁾

"Developed Markets" include United States, Canada, western Europe and Australia.

⁽²⁾⁽³⁾

"Emerging Markets" include central and eastern Europe, Latin America, Africa and the Asia Pacific region (excluding Australia).

⁽³⁾⁽⁴⁾

"Adjacent Businesses" primarily include our data center and fine art storage businesses.

Statement. Further detail of Mr. Day's severance is provided in the "Separation Agreement with Roderick Day" section of this Proxy Statement.

        Effective August 4, 2016, Mr. Stuart Brown, who joined the Company on July 25, 2016, assumed the role of Executive Vice President and Chief Financial Officer of the Company. The Compensation Committee approved the following compensation arrangement for Mr. Brown:

•

annual base salary of $550,000;



•

a $200,000 signing bonus;



•

target short-term performance-based incentive opportunity equal to 85% of annual base salary;



•

an initial award of RSUs, corresponding to approximately $900,000 in economic value;



•

an annual long-term incentive award with an initial value targeted at $1,200,000, with a pro-rated annual 2016 grant as follows:



•

RSUs corresponding to $180,000 in economic value;



•

stock options corresponding to $120,000 in economic value; and



•

PUs corresponding to $300,000 in economic value, 50% of which are correlated with total stockholder return performance over a three-year period and 50% of which are correlated with the Company's performance measured against financial goals;



•

eligibility to participate in the Company's Senior Executive Relocation Program to assist with his relocation from Denver, Colorado to the greater Boston, Massachusetts area. The amount Mr. Brown will receive under such program will not exceed $450,000, which amount includes all tax gross-up assistance; and



•

eligibility to participate in the Severance Program.

President International

        Effective March 31, 2017, Marc A. Duale resigned from his role as the Company's President, International, and the Company entered into a separation agreement and a separate advisory agreement with Mr. Duale. The separation agreement provides substantially the same severance benefits as are contained in Mr. Duale's amended and restated employment agreement. Beginning May 1, 2017, in accordance with the terms of the advisory agreement, the Company retained Mr. Duale to provide advisory services to the Company for a period of up to 12 months.

        Further information regarding Mr. Duale's agreements can be found under the "Employment Agreements" and "Separation and Advisory Agreements with Mr. Duale" sections of this Proxy Statement.

        In connection with Mr. Duale's resignation, Mr. Ernest W. Cloutier assumed the role of Executive Vice President & GM, International.

Strategic Plan

        We developed the Strategic Plan in 2013 to focus our business strategy and increase revenue. The Strategic Plan consists of three core pillars that drive our growth and maintainthe value of our business. We refer to these three pillars as the growth and strengthenvalue pillars. In addition, the Strategic Plan includes certain initiatives that are designed to improve efficiency and leverage scale to increase our dividend.dividend and support the growth and value pillars. We refer to these initiatives as the enabling activities. The

Strategic Plan's growth and value pillars, as well as the enabling activities, are represented in the following graphic:

        The table below highlights the significant 20152016 achievements with respect to each core growth and value pillar of our Strategic Plan:

Aligning Program Design with the Strategic Plan

        In connection with the continued execution of the Strategic Plan, theThe Compensation Committee periodically reviews our executive compensation programs to maintain the alignment of our incentives with our strategic objectives, including our Strategic Plan, and the creation of stockholder value. Our executive compensation programs include short-term and long-term incentive components.

        Our short-term incentive program is designed to reward all of our executive officers for executing the Company's annual operating plan and demonstrating annual progress during the year toward the Company's achievement of multi-year strategic objectives. Results are measured on a constant currency

basis to remove the effects of foreign currency exchange rate fluctuations and measure achievement primarily within the control of management. Our short-term incentive program consists of two general criteria

for evaluation:

•

evaluating the performance of our executive officers: (i) our financial performance (70% of short-term incentive opportunity): primarily rewards and (ii) the achievement of certain strategic objectives (30% of the short-term incentive opportunity).

•

For the purposes of our short-term incentive program, we measure our financial performance against targets using Adjusted OIBDAEBITDA⁽⁴⁾⁽⁵⁾ goals,⁽⁶⁾, which is our primary measure of profit;profit, revenue, and adjusted funds from operations, or AFFO⁽⁷⁾, which measures our excess cash flows used primarily to reinvest in the business and increase returns to our stockholders through dividends. Our executive officers can earn additional short-term incentive awards may be earned for profitable revenue growth in excess of targets; andtargets.



•

The strategic objectives (30% of short-term incentive opportunity):criteria rewards achievement during the year of certain objectives with respect to each core growth and value pillar of the Strategic Plan as well as other key initiatives related to real estate ownership, talentcapital efficiency, safety and safety.achievement of synergies. (For a description of these strategic objectives, see "Components of Compensation—Short-Term Performance-Based Incentives—Strategic Objectives.")

        Our long-term incentive program rewards our success over a multi-year period relative to internal financial performance targets and stockholder returns through a portfolio of stock-based awards, including:

•

Storage Revenue PUs, which reward achievement of success in storage rental revenue growth objectives, subject to achieving a minimum level of return on invested capital, or ROIC.⁽⁵⁾⁽⁸⁾ Storage rental revenue growth is a key driver of cash flow, which in turn supports growth in our

---

⁽⁵⁾

Adjusted EBITDA is defined as income (loss) from continuing operations before interest expense, net, provision (benefit) for income taxes, depreciation and amortization, and also excludes certain items that we believe are not indicative of our core operating results, specifically: (i) loss (gain) on disposal/write-down of property, plant and equipment (excluding real estate), net; (ii) intangible impairments; (iii) other expense (income), net; (iv) gain on sale of real estate, net of tax; (v) operating expenditures associated with our acquisition of Recall, including advisory and professional fees and costs to complete the divestments required in connection with receipt of regulatory approval and to provide transitional services required to support the divested businesses during a transition period, as well as operating expenditures to integrate Recall with our existing operations, including moving, severance, facility upgrade, REIT conversion and system upgrade costs, or Recall Costs; and (vi) costs associated with our conversion to a REIT, excluding REIT compliance costs beginning January 1, 2014, or REIT Costs.



⁽⁶⁾

We changed the name of the Adjusted OIBDA metric to Adjusted EBITDA. The calculation of Adjusted EBITDA produces the same results as the calculation of Adjusted OIBDA; therefore, our targets and the evaluation of achievement did not change for compensation purposes.



⁽⁷⁾

AFFO is defined as net income excluding depreciation on real estate assets, gain on sale of real estate, net of tax, loss (gain) on disposal/write-down of property, plant and equipment (excluding real estate), net, intangible impairments, other expense (income), net, deferred income taxes and REIT tax adjustments, Recall Costs, REIT Costs, loss (income) from discontinued operations, net of tax, loss (gain) on sale of discontinued operations, net of tax, non-cash rent expense or income, plus depreciation on non-real estate assets, amortization expense of customer relationship intangible assets and deferred financing costs, stock-based compensation expense and the impact of reconciling to normalized cash taxes, less maintenance capital expenditures and non-real estate investments, excluding Recall integration capital expenditures.

⁽⁸⁾

ROIC is defined as net operating profit after taxes plus depreciation and amortization less non growth capital expenditures divided by the average of the beginning and ending balance of total debt plus stockholders equity and non controlling interest less cash plus accumulated depreciation on racking.




dividend. Due, in part, to the three-year performance period of our Storage Revenue PUs, beginning in 2016 results are measured on a reported basis and includewithout regard to the effect of currency fluctuation;

•

Relative TSR PUs, or TSR-Based PUs, which reward total stockholder return, or TSR, performance, including the impact of changes in share price and reinvested dividends, relative to the majority of the S&P 500 over a three-year period;

•

Stock Options, which reward share price growth. Our stock optionsoption awards generally have an exercise price equal to the closing price on the date of grant, or the Fair Market Value, of our stock at the date of grant, but our CEO's stock optionsoption awards, since 2014, have had an exercise price 25% above the Fair Market Value at the date of grant. Stock options vest ratably over three years and are generally exercisable until the tenth anniversary of the grant date; and

•

Restricted Stock Units, or RSUs, which support retention and provide additional alignment with stockholders and vest ratably over three years.

        The Compensation Committee annually evaluates our incentive programs to ensure they continue to support ourthe Strategic Plan and adopts changesmodifications where appropriate. In 20152016 the Compensation

⁽⁴⁾

Adjusted OIBDA is defined as operating income before depreciation, amortization, intangible impairments, (gain) loss on disposal/write-down of property, plant and equipment, net (excluding real estate), Recall Costs and REIT Costs. "Recall Costs" include operating expenditures associated with our proposed acquisition of Recall, including costs to complete the Recall acquisition, including advisory and professional fees, as well as costs incurred to integrate Recall with our existing operations, including moving, severance, facility upgrade, REIT conversion and system upgrade costs. "REIT Costs" include costs associated with our conversion to a REIT, excluding REIT compliance costs beginning January 1, 2014 which we expect to recur in future periods.

⁽⁵⁾

ROIC is defined as net operating profit after taxes plus depreciation and amortization less non-growth capital expenditures divided by the average of the beginning and ending balance of total debt plus stockholders equity and non-controlling interest less cash plus accumulated depreciation on racking.

Committee approved a series of refinements to better align our incentive programs with ourthe Strategic Plan, including:

•

adding AFFO as a key component of measuring financial performance;



•

refining the strategic measures contained in the short-term performance-based incentive program:



•

we selected Days Sales Outstanding, or DSO, as a capital efficiency measure to drive improvement in our Developed Markets, we now utilize storage revenue internal growth, which reflects both volume growththe cash collection cycle and pricing, to measure achievement;encourage cash flow benefit that results from a lower DSO; and



•

following the acquisition of Recall, we now consider a metric related toachieved synergies associated with the realization of certain security and safety related objectives to measure achievement;Recall acquisition; and



•

implementing the second phase ofmodifying our long-term incentive strategy, adopted in 2014, and refined our performance metric to reflect our conversion to a real estate investment trust, or REIT:



•

we granted TSR-BasedStorage Revenue PUs to a broad groupmeasure results without regard to currency fluctuation reflecting the Compensation Committee's determination that constant currency best reflects the performance of executives, including all of our executive officers, consistent with our long-term incentive strategy adopted in 2014; and



•

we changed the revenue metric of certain of our PU awards to storage rental revenue from total revenue.

management.

20152016 Compensation Decisions & Performance

Pay Opportunity

        Following its annual review of performance for 2016, executive development and relevant market benchmark data, the Compensation Committee approved increases in pay opportunity for certain of our Named Executive Officers, including our CEO. In each case, the majority (or, in the case of our CEO, the entirety) of the increase in pay opportunity was delivered through variable compensation,

which increased the proportion of compensation tied to achievement of performance goals or stock price appreciation.

Performance & Compensation Results

        OurFor 2016, both our short-term and long-term incentive awards reflect operational performance without regard to currency fluctuation, butfluctuation; however, our long-term incentive awards aregranted in 2014 and 2015 will continue to be measured on reported results. Following the acquisition of Recall, all of our outstanding incentive awards were adjusted to reflect the expected impact of the Recall acquisition.

        In 2015,2016, our operationalfinancial performance, after adjusting for the impact of acquisitions during the year and measured in constant currency exceededand performance against strategic objectives, on average, did not achieve 100% of the goals on average, established by the Compensation Committee. Consequently, the pay-for-performance structure ofCommittee, but our executives exceeded expectations relative to their individual goals and objectives. Combining financial performance with individual performance, our variable compensation programs delivered above target short-term incentive awards. On average, our short-term incentive awards achieved 119.35%114% of target; primarily as a result oftarget calculated based on the following operational results:

•

Adjusted OIBDA was 102.6%EBITDA and revenue achieved a combined payout of 91% of target reflecting our focus on continuous improvement and the early impactdue primarily to Adjusted EBITDA performance at 99.5% of the Transformation Program;target;



•

enterprise revenueAFFO performance was 99.3%102.5% of target, reflecting improved internal growth; however, they were below the targets set by our Compensation Committee;which resulted in a payout of 115.5% of target; and



•

strategic objectives, on average, achieved 94%a combined payout of target performance with five84% of the six metrics meeting or exceeding target performance.target; and

•

the Compensation Committee approved individual performance modifiers based on performance against individual goals and objectives as well as individual efforts related to completing the Recall acquisition and progress on the related integration of Recall that, on average, added 18% to the combined financial and strategic performance results discussed above.

        Our long-term incentive awards benefited from the increase in our share price during 2016; however, certain of our performance units granted in 2014 and 2015, which are measured on reported results, werecontinue to be negatively impacted by the strengtheningstrong U.S. dollar and the decline in our share price.dollar. As a result, long-term incentives, on average, are tracking significantly below the potential economic value at the time of their grant, which corresponds with the experience of our stockholders as measured over the same time period:grant:

•

our TSR during 20152016 was approximately –25.7%27.7% relative to 1.4%12.0% for the S&P 500 Total Return Index;



•

Mr. Meaney's 2013 TSR-Based PUs did not meetwith a performance period ending in 2016 earned 138% of target shares, reflecting performance during the minimum performance threshold ofrelevant period at the 30^th69th percentile of the S&P 500, excluding financial services companies, during companies;



•

the PUs with a performance period and,ending in 2016, which were based on Total Revenue & ROIC performance for the three year period ending in 2016, did not meet the minimum performance level due primarily to currency fluctuation; as a result, no shares were earned under this award; and



•

the various PUs awarded during 2014 and 2015, for which the performance periods have not been completed, are currently forecast, on average, to pay significantly below the potential economic value at the time of their grant, which reflects the impact of share price decline, negative foreign currency impacts and revenue growth underperforming the goals set by the Compensation Committee, without regard to currency fluctuation.earned.

Realizable Pay Analysis

        Realizable pay reflects actual bonuses earned and the current value of equity awards, which are subject to adjustment based on changes in our share price and the achievement of performance goals. The Compensation Committee and the Company believe a realizable pay analysis with respect to our CEO is a valuable data point to evaluate the pay-for-performance effectiveness of our compensation programs and to evaluate the directional alignment of our equity awards with the experience of our stockholders.

        The realizable pay analysis compares realizable pay, or Realizable Pay, to pay opportunity, or Pay Opportunity, in the context of our operational performance and the performance of our Common Stock, where:

•

Pay Opportunity represents the target value of compensation awarded for each year and includes base salary, target bonus and the potential economic value of equity awards as measured at the date of grant; and



•

Realizable Pay represents the current value of Pay Opportunity adjusted for achievement relative to performance goals, changes to our share price and the amount of dividends accrued on certain of our equity awards.

        The table below illustrates the relationship between the Pay Opportunity of our CEO for fiscal 2013, 2014, 2015 and 20152016 and the realizable value of that compensation measured at the end of 2015.2016. Over the three-yearfour-year period ending on December 31, 2015,2016, total Realizable Pay represents approximately 68%86% of

Pay Opportunity, primarily reflecting the underperformance, on average, of our PU awards, and the impact of our share price performance on other stock-basedpremium

priced stock options, partially offset by the underperformance, on average, of our PU awards. All values below are shown in thousands.

        Pay Opportunity—equals, for each of fiscal 2013, 2014, 2015 and 2015:2016: (1) annual base salary for the applicable fiscal year,plus (2) target bonus for the applicable fiscal year,plus (3) the potential economic value of equity awards approved during the applicable fiscal year by the Compensation Committee (as measured at the date of grant). No target value is included for items reported in the "All Other Compensation" column of the Summary Compensation Table.

        Realizable Pay—equals, for each of fiscal 2013, 2014, 2015 and 2015:2016: (1) annual base salary for the applicable fiscal year,plus (2) actual paid bonus for the applicable fiscal year,plus (3) in-the-money value of stock options granted during the applicable year,plus (4) value of RSUs granted during the applicable fiscal year, including accrued dividends thereon,plus (5) value of PUs granted during the applicable fiscal year, reflecting actual achievement for awards granted in fiscal 2013 and 2014 and estimated performance as of the end of Fiscal 2015fiscal 2016 for awards granted in fiscal 20142015 and fiscal 20152016 (accordingly, the actual number of PUs that may be credited under these programs will vary). All stock values are calculated using the closing price of our Common Stock as of December 31, 2016.

2017 Updates

CEO Pay Opportunity

        In connection with its annual compensation program review, the Board approved an increase to Mr. Meaney's pay opportunity for 2017 and adopted a two-year transition to the mix of his long-term incentive awards.

TSR-Based PUs

        Effective for the TSR-Based PUs granted in 2017, the Company's TSR performance will be measured against the companies on the MSCI US REIT Index as the comparator group. For awards granted in prior years, the comparator group had been the S&P 500, excluding financial services companies. The Compensation Committee selected the MSCI US REIT Index for 2017 grants because this index is a more reflective benchmark for relative TSR performance given the Company's REIT status.

Say-on-Pay Vote Response and Stockholder Engagement

        We have an annual stockholder advisory vote on executive compensation, a "say-on-pay" vote, to provide stockholders with an additional tool to voice their opinions about executive compensation, with a goal of maintaining an alignment of interests between our stockholders and our executives. The Compensation Committee considered the results of the advisory vote by stockholders on the "say-on-pay" proposal presented to stockholders at the Company's 20152016 Annual Meeting of Stockholders. As in previous years, there was overwhelming support at the 20152016 annual meeting for the compensation program offered to the Company's Named Executive Officers, with approximately 98%97% of votes cast in favor. Accordingly, in 2015,2016, the Compensation Committee made no direct changes to the Company's executive compensation programs as a result of the say-on-pay vote at the Company's 20152016 Annual Meeting of Stockholders.

        In early 2016, the Company's management conducted outreach with certain stockholders related to our executive compensation. Even though we have received significant support from stockholders through our say-on-pay votes, the Company and the Compensation Committee believes it is important to periodically engage directly with our stockholders in order to gain a better understanding of our stockholders' views on our executive compensation practices. We ultimately engaged with stockholders representing 35% of our outstanding shares of Common Stock, and the stockholders with whom we communicated reiterated their support for our approach to executive compensation while sharing their perspective on what they most value in executive compensation programs. The findings were reported to and considered by the Compensation Committee in connection with its annual review of our incentive plans.

        Our executive compensation programs reflect a number of best practices implemented by the Compensation Committee in recent years, including:

•

compensation clawback policy;

•

executive and director stock ownership requirements, which exclude unvested and unearned shares, including a requirement to retain certain shares until the requirement is met;



•

between 71% and 87% of our Named Executive Officers' target direct compensation is at-risk;



•

"double trigger" feature, requiring both a change in control and termination of employment before the acceleration of vesting of awards granted under both the 2002 Plan and the 2014 Plan;



•

a prohibition on hedging or pledging of shares of Common Stock;



•

the Compensation Committee retains an independent compensation consultant;



•

we do not offer excise tax gross-ups in connection with a change in control;



•

we do not offer pensions or supplemental executive retirement plans; and



•

limited use of executive perquisites that recognize standard local practices in international markets.

        In early 2016, the Company's management conducted outreach with certain stockholders related to our executive compensation. Even though we have received significant support from stockholders through our say-on-pay votes, the Company and the Compensation Committee believes it is important to periodically engage directly with our stockholders in order to gain a better understanding of our stockholders' views on our executive compensation practices. We ultimately engaged with stockholders representing 35% of our outstanding shares of Common Stock, and the stockholders with whom we communicated reiterated their support for our approach to executive compensation while sharing their perspective on what they most value in executive compensation programs. The findings were reported to and considered by the Compensation Committee in connection with its annual review of our incentive plans.

Compensation Philosophy and Design Principles

        The purpose of our executive compensation programs is to attract, retain and focus the talents and energies of executives, including our Named Executive Officers, on meeting the current and future objectives of the Company, most notably the creation of stockholder value. The design principles that govern our Named Executive Officer compensation programs are described below.

        General program competitiveness—Our compensation program serves to attract and retain top performing executive officers. All of our executive compensation programs target pay levels are established with reference to relevant market data to evaluate their competitiveness. The relative position of each Named Executive Officer's compensation compared to the market data referenced reflects his or her experience and proficiency in performing the duties of his or her position.

        Pay for performance—A substantial percentage of each Named Executive Officer's total compensation opportunity is contingent on annual and multi-year performance, as discussed above under the heading "Aligning Program Design with the Strategic Plan." If performance exceeds the target, then an award can pay out in excess of the target value. Conversely, if performance does not achieve the target, compensation can fall below an award's target level and, in fact, be as low as zero.

        Internal parity—The total compensation opportunity for each Named Executive Officer reflects the responsibility, scope and complexity of that individual's role within the Company.

        Stockholder alignment—Our compensation programs for our Named Executive Officers align with the interests of our stockholders by emphasizing performance criteria that drive both short-term results and long-term stockholder value creation. Our Named Executive Officers, including our CEO, are also subject to minimum share ownership requirements, as discussed under the "Executive Stock Ownership Guidelines" section of this Proxy Statement.

        Alignment with various business strategies—Beginning in 2014, we structured our executive compensation programs primarily to provide common rewards for the achievement of enterprise financial goals and strategic objectives. Our annual short-term incentive program continues to provide for individual differentiation reflecting each executive's responsibility for the performance of such executive's function's or business unit's contribution toward the common goals, and such executive's bonus may be adjusted according to achievement versus individual objectives.

Establishing Compensation

Process

        In applying our compensation philosophy and design principles to establish appropriate compensation programs and target compensation levels, the Compensation Committee:

•

Annually approves a recommendation to the Board for the salary, short-term and long-term incentive compensation for our CEO. The Compensation Committee's recommendation reflects (1) an analysis of the Company's performance against predetermined financial goals and its evaluation of our CEO's performance against predetermined individual objectives, (2) performance feedback from our CEO's direct reports, which is also shared with other members of the Board and (3) input from members of the Board. The Compensation Committee's recommendation is then presented to the independent members of the Board for approval.



•

Annually reviews and approves the salary, short-term and long-term incentive compensation for our other Named Executive Officers.



•

Annually reviews and approves the structure of our short-term and long-term incentive programs for all Named Executive Officers, including performance metrics, performance and payout grids and the weighting applied to each metric. The review typically balances an internal and external perspective developed in collaboration with members of management and the Compensation Committee's independent compensation consultant. Based upon this review, the Compensation Committee may maintain or modify the amount and mix of grants under our incentive programs.



•

Annually establishes the individual goals and objectives utilized in our short-term incentive program for our CEO and reviews the individual goals for the other Named Executive Officers recommended by our CEO.



•

Periodically evaluates the effectiveness and competitiveness of other executive compensation programs, such as executive benefits, perquisites and our severance policies. These periodic evaluations are conducted to ensure alignment with our internal strategy and objectives and to consider external market practices.



•

Annually establishes the financial performance goals that are utilized in our short-term and long-term incentive plans. The annual financial performance targets are initially based upon our annual operating plan approved by the Board, assuming constant currency, and may be adjusted during the year. The multi-year performance targets are aligned with achieving our Strategic Plan. When the financial targets are set, the Compensation Committee approves a policy which identifies the nature of potential adjustments to the target levels that may be considered throughout the fiscal year. Our internal audit team reviews the potential adjustments and reports

the results to our AuditCompensation Committee. The Compensation Committee considers these reports and may adjust financial targets based on the adjustment factors approved at the beginning of the year.

        In 2015,2016, the Compensation Committee approved adjustments to performance goal targets, or the Adjustment Factors, to (1) eliminate the effects of unbudgeted acquisitions, primarily the acquisition of Recall, (2) eliminate the effects of

rent reduction resulting from lease conversions and (3) exclude the costs associated with our proposed acquisition of Recall from our Adjusted OIBDA calculation.Recall. The Adjustment Factors apply to short-term performance-based compensation awarded in 20152016 and long-term PUs that isare subject to relevant goal targets.

        The net effect of applying the Adjustment Factors to the revenue targettargets increased the targetthose targets by 0.4%16.0%. TheIn particular, the net effect of applying the Adjustment Factors increased Adjusted OIBDA performanceEBITDA and AFFO targets by 5.0%14.8% and 21.6%, on average.respectively.

Role of Named Executive Officers

        Our Named Executive Officers assist the Compensation Committee in carrying out its duties throughout the year by completing specific tasks, including:

•

our CEO establishes the individual goals and objectives for the Named Executive Officers (other than himself). He proposes his own individual goals and objectives, with input from the Board, which are then approved by the Compensation Committee;



•

our CEO develops compensation recommendations for the Named Executive Officers (other than himself) for the Compensation Committee's review, including salary levels, the potential economic value of long-term incentives and achievement of individual goals and objectives; and



•

each Named Executive Officer prepares a self-review to assist the review of his performance against individual goals and objectives, which self-review is shared with the Compensation Committee for the CEO and with the CEO for the other Named Executive Officers.

Role of Consultants

        The Compensation Committee has retained the services of an independent compensation consultant to provide ongoing advice and perspective to the Compensation Committee in the following areas related to the compensation of our Named Executive Officers:

•

market pay analyses and market trends;



•

assistance with the review and selection of a group of business services companies, or the Custom Peer Group, to serve as a reference point for the market analyses;



•

ongoing support with regard to the latest relevant regulatory, technical and/or accounting considerations affecting compensation and benefit programs;



•

assistance with the design of executive compensation or benefit programs, as needed; and



•

preparation for and attendance at selected Compensation Committee meetings.

        Since May 2012, the Compensation Committee has engaged Pay Governance LLC, or Pay Governance, to assist the Compensation Committee by providing ongoing executive compensation consulting. Pay Governance reports directly to the Compensation Committee, has regular meetings with the chairperson of the Compensation Committee and meets with the Compensation Committee in executive session.

        Pay Governance does not provide any other services to the Company except providing assistance on director compensation matters for the Nominating and Governance Committee. The Compensation

Committee has reviewed the nature of the relationship with its independent compensation consultants and determined that there were no conflicts that impacted the advice and guidance provided to the Compensation Committee.

Benchmarking

        To provide an external perspective relative to executive compensation levels, plan design trends and market best practices, the Compensation Committee reviews market analyses prepared by its independent compensation consultant. Given the nature of our business and our market leading position, there is no ideal group of companies that reflects direct business competitors or competitors for talent. The Compensation Committee has elected to develop a group of business services companies, or the Custom Peer Group, to serve as a reference point for the market analyses.Group.

        The Compensation Committee, in collaboration with our compensation consultant and management, annually reviews the Custom Peer Group for continued applicability and has developed the Custom Peer Group below based on the following criteria:

•

comparable revenue size and industry;



•

similar market capitalization;



•

pays regular quarterly dividends; and



•

similar degree of global operations.

        The 20152016 Custom Peer Group includes the following companies, with an asterisk noting the newly added companies:company:

        The median 2013 revenue ofin 2014, the most recent full year available when the 2016 Custom Peer Group was $3.4determined, was $3.1 billion compared tofor both the Company's 2013 revenue of $3.0 billion.2016 Custom Peer Group and the Company. The 20152016 Custom Peer Group, as compared to the 20142015 Custom Peer Group, reflects (1) the removal of ADP due to its larger revenue size,Quad/Graphics and (2) the removal of Lender Processing Services due to its recent acquisition by Fidelity National Financial and (3) the addition of Digital Realty Trust and Prologis, each ofEquinix, which is a REIT in the data center storage industry that met the criteria described above.

How We Use Market Data

        Pay levels—Market data is one element considered by the Compensation Committee when making compensation decisions, but the Compensation Committee does not set compensation levels based solely on market data. Rather, the Compensation Committee reviews the 25^th, 50^th and 75^th percentiles of relevant market data as one frame of reference in making its compensation decisions. Final compensation decisions reflect a variety of factors, including each executive's experience, performance rating, the relative importance of the executive's role within the organization, as well as where each executive's pay level falls relative to the market data.

        Plan design—When designing or assessing the design of our compensation programs, the Compensation Committee reviews programs of the Custom Peer Group to establish typical market practice. The Compensation Committee evaluates our specific circumstances and business objectives and follows market practice with respect to the design of our programs where appropriate but may deviate from market practice where the Compensation Committee deems it is in the best interest of the Company and our stockholders.

Role of Consultants

        The Compensation Committee has retained the services of an independent compensation consultant to provide ongoing advice and perspective to the Compensation Committee in the following areas related to the compensation of our Named Executive Officers:

•

market pay analyses and market trends;





•

assistance with the review and selection of the Custom Peer Group;



•

ongoing support with regard to the latest relevant regulatory, technical and/or accounting considerations affecting compensation and benefit programs;



•

assistance with the design of executive compensation or benefit programs, as needed; and



•

preparation for and attendance at selected Compensation Committee meetings.

        Since May 2012, the Compensation Committee has engaged Pay Governance LLC, or Pay Governance, to assist the Compensation Committee by providing ongoing executive compensation consulting. Pay Governance reports directly to the Compensation Committee and has regular meetings with the chairperson of the Compensation Committee.

        Pay Governance does not provide any other services to the Company except providing assistance on director compensation matters for the Nominating and Governance Committee. The Compensation Committee has reviewed the nature of the relationship with its independent compensation consultants and determined that there were no conflicts that impacted the advice and guidance provided to the Compensation Committee.

Components of Compensation

        Our Named Executive Officers' total direct compensation, or TDC, is designed to reward our Named Executive Officers based on achievement of financial and strategic goals and returns to stockholders and consists of base salary, target bonus and long-term incentive grant value.

        As depicted below, approximately 87% of our CEO's target TDC, and, on average, 71% of our other Named Executive Officers' target TDC (where applicable, excluding the value of new hire inducement equity awards), is tied directly to the achievement of financial goals, strategic objectives or stock price appreciation through our short-term and long-term incentive programs.

CEO		Other Named Executive Officers

        Below is a summary of the elements, objectives, risk mitigation factors and key features of our TDC program for our Named Executive Officers. A more detailed discussion of each element and the associated pay decisions follows this section.

•

Base salary and benefits are designed to attract and retain highly qualified individuals; in order to avoid excessive risk taking, it is important that not all cash compensation be variable.



•

Annual cash short-term incentive compensation awards are designed to focus the entire senior executive team, including the Named Executive Officers, toward achieving enterprise goals while recognizing their individual contributions, including:



•

attaining financial goals in line with our annual budget;



•

achievement of strategic objectives;



•

performance relative to initiatives in areas within their control; and



•

rewarding outstanding individual performance.



•

Our short-term incentive awards are expressed as a percentage of base salary, and the amount of compensation payable under each award is subject to a maximum payout; short-term incentive awards are also subject to our clawback policy described below under the "Executive Compensation Clawback" section of this Proxy Statement.



•

Long-term equity incentives are designed to:



•

align the interests of our executive officers with our stockholders;



•

reward overall enterprise performance; and



•

encourage the retention of our executive officers by providing additional opportunities for them to participate in the ownership of the Company and its future growth.



•

Our long-term incentive awards are granted in the form of PUs, RSUs and stock options. Generally, PUs are subject to cliff vesting three years from the date of the original grant and

settle in shares of our Common Stock. RSUs and stock options typically vest ratably over three years (with certain exceptions described below) and are settled in shares of our Common Stock. Equity awards are also subject to our clawback policy described below the "Executive Compensation Clawback" section of this Proxy Statement.

        In addition to the TDC elements described above, our U.S.-based executives participate in the retirement and welfare benefits generally available to our full-time employees, such as medical, dental, life insurance, 401(k) Plan, the 2013 ESPP, and other fringe benefits, some of which are more fully described below:

•

our 401(k) Plan allows our Named Executive Officers to contribute up to 25% of their "plan" compensation, subject to certain regulatory limits. Under our 401(k) Plan, we generally match 50% of the first 4% of compensation contributed by our Named Executive Officers, up to $5,300 for 2015.2016.



•

the 2013 ESPP provides all of our employees in the U.S. and Canada with the opportunity to acquire an equity interest in the Company by providing favorable terms upon which they may purchase our Common Stock.

        In addition, our U.S.-based Named Executive Officers are eligible for certain executive benefits, including a voluntary deferred compensation program and limited perquisites, which are included in the "All Other Compensation" column of the Summary Compensation Table and related footnote appearing in this Proxy Statement.

        Also, our Executive Deferred Compensation Plan, or the EDCP, allows our Named Executive Officers to defer some of their base salary and/or cash incentive compensation in amounts in excess of the amounts they can defer under our 401(k) Plan. The Company does not provide contributions under the EDCP. The EDCP is intended to encourage the continued employment of the participating employees and to facilitate the recruiting of executive officers and other highly compensated employees required for our continued growth and profitability. Mr. Day did not, and Messrs. Day, Duale and Keddy do not, participate in the 401(k) Plan, the 2013 ESPP or the EDCP but each receivesbecause they are not U.S.-based executives. Instead, Mr. Day received, and Messrs. Duale and Keddy receive, additional benefits that are customary for executives in their respective work locations as more fully discussed under the "—Employment Agreement with Mr. Day", "—Employment Agreement with Mr. Duale" and "—Employment Agreement with Mr. Keddy" sections of this Proxy Statement.

Base Salary

        The table below details the annualized base salaries, and any year-over-year increase, for each of our Named Executive Officers as measured at the end of each of 20142015 and 2015.2016. The increases were effective in March 2015, except that Mr. Keddy received a partial increase in March 2015 and a partial increase effective in April 2015, as further described below.2016. Consistent with typical market practice, in 20152016 our CEO received a higher base salary than the other Named Executive Officers. This is due primarily to the greater responsibility experience and oversight duties of the CEO as compared to the other Named Executive Officers.

        TheMr. Meaney's base salary increase provided to Mr. Day reflects his performance and development since his appointment as chief financial officer of the Company in March 2014 and his position relative to the relevant market benchmarks. The base salary increase for Mr. Keddy reflects a 3% merit increase effective March 2015 in his prior role and the remainder of the increase effective in April 2015 reflecting the additional responsibilities he assumed in his new role as EVP & GM, North America & Western Europe. Ms. Evens's base salary was set in connection with her appointment as EVP, Chief People Officer in July 2015 reflecting her experience, expected contributions and compensation with her previous employer as well as her position relative to the market benchmarks.

        The base salary of each of Mr. Meaney and Mr. Duale remained unchanged in 2015.2016. The Compensation Committee determined that the base salary of Mr. Meaney was appropriately positioned based on the factors considered by the Compensation Committee and determined that any increase in TDC would be best delivered through our variable compensation programs.

        Mr. Brown's base salary was set in connection with his appointment as Executive Vice President and Chief Financial Officer in August 2016 reflecting his experience, expected contributions and compensation with his previous employer as well as his position relative to the market benchmarks.

        Mr. Duale's base salary remained unchanged in 2016. Mr. Duale's base salary is positioned above the 75^th percentile of market data, largely due to his depth of experience in leading international businesses prior to joining the Company, and reflects the compensation that was necessary to entice him to join the Company. Mr. Duale's salary has not been increased since 2009 in recognition of his position relative to both external market data and internal parity.

        The base salary increase for Mr. Cloutier reflects his performance and increased responsibility after assuming the role of general manager of our U.S. federal business.

        The base salary increase for Mr. Keddy reflects his performance since his appointment in April 2015 as EVP & GM, North America & Western Europe and his position relative to the relevant market benchmarks.

        The base salary increase provided to Mr. Day reflects his performance and development since his appointment as chief financial officer of the Company in March 2014 and his position relative to the relevant market benchmarks.

Short-Term Performance-Based Incentive Compensation

Target Incentives

        Our Named Executive Officers participate in the Company's short-term performance-based incentive compensation programs. The Compensation Committee annually reviews the target short-term incentive opportunity for each Named Executive Officer and approves a new target, when appropriate. Short-term incentive compensation opportunities are expressed as a percentage of each Named Executive Officer's base salary. For 2015,2016, these percentages were:

        The percentage of Mr. Meaney's 2015 total direct compensationBrown's 2016 short-term incentive opportunity was set at 85% of base salary in connection with his appointment as EVP, Chief Financial Officer in August 2016.

        The percentage of Mr. Cloutier's 2016 attributable to short-term incentive opportunity increased ten percentage points to 135%80% of base salary, reflectingsalary. This increase reflects an increase in Mr. Cloutier's TDC as a result of his performance and a commensurate increase in short-term incentive opportunity due to the Compensation Committee's evaluationdesire to structure the majority of his performance, relevant market benchmarks and the Compensation Committee's intent to deliver total direct compensation increasesincrease through our variable compensation programs.

        The percentage of Mr. Keddy's 2015 total direct compensation attributable to2016 short-term incentive opportunity increased ten percentage points to 70%80% of base salary, effective April 2015,salary. This increase reflects an increase in connection withMr. Keddy's TDC as a result of his performance since his appointment as EVP & GM, North America & Western Europe.

Europe in 2015 and a commensurate increase in short-term incentive opportunity due to the Compensation Committee's desire to structure the majority of his compensation increase through variable programs.

        The percentage of Ms. Evens' 2015 total direct compensation attributable to short-term incentive opportunity was set at 60% of base salary in connection with her appointment as EVP, Chief People Officer in July 2015. In addition, Ms. Evens was provided a signing bonus of $200,000 as an inducement to join the Company in recognition of cash compensation that she forfeited when leaving her previous employer.

        The percentage of 20152016 salary attributable to short-term incentive opportunity for the other Named Executive Officers is, in each case, unchanged from 2014.2015. The Compensation Committee determined that each target opportunity represented the appropriate amount of short-term compensation at risk for each Named Executive Officer based on his or her role, impact on the Company's results and market comparisons. In 2015,2016, Mr. Meaney's target opportunity was the largest among the Named Executive Officers because he was most accountable for the Company's performance, and the Compensation Committee determined it was important to provide a greater portion of his cash compensation through a variable program. The target short-term incentive compensation opportunity for other Named Executive Officers is a lower percentage of their base salary, reflecting their mix of compensation, expected impact on the performance of the Company and market practice for their role.

Program Structure

        Achievement of the target short-term incentive opportunity for each Named Executive Officer is based upon (1) the Company's performance against targeta series of financial goals, (2) the Company's performance against a series of strategic objectives and (3) personal performance against the individual goals and objectives of the respective Named Executive Officer set at the beginning of the year, as illustrated below. All members of the senior executive team, including the Named Executive Officers, have the same target financial goals and the same financial and strategic objectives, which serve to align the senior executive team toward the same enterprise goals. The individual modifier component, however, allows for recognition of individual performance and contributions. In support of our philosophy of paying for performance, actual short-term incentive awards for our Named Executive Officers may range from 0% to a maximum of 167.5%, which can be reached when achieving maximum performance against all measures. of incentive opportunity. Where relevant, results are measured in constant currency to better reflect management's influence on results during the applicable year.