Document:

EX-10.18

 Exhibit 10.18 

STOCKHOLDERS AGREEMENT 

STOCKHOLDERS AGREEMENT (this “Agreement”), dated as of
            , 2014, between Zayo Group Holdings, Inc., a Delaware corporation (the “Company”), on the one hand, and each Sponsor (as defined below) listed on the signature
pages hereto and each stockholder listed on the signature pages hereto, solely with respect to Articles I, III and IV of this Agreement (collectively, and together with the Sponsors, the “Participants”), on the other hand, and any
other Person that may become a party to this Agreement after the date and pursuant to the terms hereof. 
 WHEREAS, concurrently with the
effectiveness of this Agreement, the Company has consummated the Restructuring (as defined below) and an initial Public Offering of its common stock (the “IPO”); and 

WHEREAS, each Participant desires to enter into this Agreement, severally, as to such Participant, and not jointly, to set forth the
respective rights and obligations of the Company and such Participant. 
 NOW, THEREFORE, in consideration of the mutual agreements
contained herein, the parties hereto hereby agree as follows: 
 ARTICLE I 

DEFINITIONS 
 1.1
Certain Definitions. 
 “Affiliate,” with respect to (a) a Participant, means (i) any Person that, directly
or indirectly, through one or more intermediaries, is in control of, is controlled by, or is under common control with, such Participant, (ii) any Person who is a general partner, manager, director or officer (A) of such Participant or
(B) of any Person described in clause (i) above, or (iii) any affiliated funds advised or managed by the same investment manager (or any of its Affiliates) as such Participant, and (b) the Company, means (1) any Person that,
directly or indirectly, is in control of, is controlled by, or is under common control with, the Company or (2) any Person who is a general partner, manager, director or officer (A) of the Company or (B) of any Person described in
clause (1) above and (C) any natural person, any member of the Immediate Family of such person. For purposes of this definition, “control” (including with correlative meanings, the terms “controlling”, “controlled
by” and “under common control with”) of a Person shall mean the power, directly or indirectly, (y) to vote 50% or more of the securities having ordinary voting power for the election of directors of such Person whether by
ownership of securities, contract, proxy or otherwise, or (z) otherwise to direct or cause the direction of the management and policies of such Person whether by ownership of securities, contract, proxy or otherwise. 

“Aggregate ATP Equity Security Amount” has the meaning set forth in Section 3.5. 

“Agreement” has the meaning set forth in the preamble. 

 “Alternative Transfer Protocol” has the meaning set forth in
Section 3.1(a). 
 “Alternative Transfer Protocol Notice” has the meaning set forth in Section 3.5(a). 

“Applicable Law” means all applicable provisions of constitutions, treaties, statutes, laws (including the common law),
rules, regulations, ordinances, codes or orders of any Regulatory Entity, any consents or approvals of any Regulatory Entity and any orders, decisions, injunctions, judgments, awards, decrees of or agreements with any Regulatory Entity. 

“Board” has the meaning set forth in Section 2.1(a). 

“Business Day” means any day that is not a Saturday, a Sunday or other day on which banks are required or authorized by law
to be closed in the city of New York, New York. 
 “Charlesbank Investor” means, collectively, Charlesbank Equity Fund VI,
Limited Partnership, CB Offshore Equity Fund VI, Limited Partnership, Charlesbank Equity Coinvestment Fund VI, Limited Partnership and Charlesbank Equity Coinvestment Partners, Limited Partnership, together with any of its Permitted Transferees that
as of any applicable time of determination owns Equity Securities. 
 “CII” means Communications Infrastructure
Investments, LLC, a Delaware limited liability company and the direct parent of the Company prior to the Restructuring and the IPO. 

“Common Stock” means the common stock, $0.001 par value per share, of the Company, and any securities issued in respect
thereof, or in substitution therefor, in connection with any stock split, dividend or combination, or any reclassification, recapitalization, merger, consolidation, exchange or other similar reorganization. 

“Company” has the meaning set forth in the preamble. 

“Effective Time” has the meaning set forth in Section 4.2. 

“Eligible Designee” has the meaning set forth in Section 2.1(a). 

“Equity Securities” means any and all shares of Common Stock of the Company, securities of the Company convertible into, or
exchangeable or exercisable for, such shares, and options, warrants or other rights to acquire such shares, in each case, acquired prior to or on the date of this Agreement. 

“Exchange Act” means the Securities Exchange Act of 1934, as amended from time to time, and the rules and regulations
promulgated thereunder. 
 “Follow-on Offering” has the meaning set forth in Section 3.3. 

“GTCR Investor” means, collectively, GTCR Fund X/A LP, GTCR Fund X/C LP and GTCR Co-Invest X LP, together with any of its
Permitted Transferees that as of any applicable time of determination owns Equity Securities. 

  
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 “Hedging Transaction” has the meaning set forth in Section 3.1(a). 

“Immediate Family” means, with respect to any natural person, each of such person’s lineal descendants and ancestors,
spouse, brothers, and sisters, including adoptive relationships, or any trust or entity formed for estate planning purposes or a private foundation for the benefit of the foregoing Persons. 

“Independent Director” means an “independent director” as such term is defined from time to time in the corporate
governance rules for NYSE-listed companies. 
 “IPO” has the meaning set forth in the recitals. 

“Lock-up Agreement” has the meaning set forth in Section 3.1(a). 

“Lock-up Period” has the meaning set forth in Section 3.1(a). 

“Minimum Charlesbank Ownership Threshold” has the meaning set forth in Section 2.1(a). 

“Minimum GTCR Ownership Threshold” has the meaning set forth in Section 2.1(a). 

“Nominating Committee” means the Nominating and Governance Committee of the Board. 

“Participants” has the meaning set forth in the preamble. 

“Participant ATP Equity Security Amount” has the meaning set forth in Section 3.5(b). 

“Permitted Transferee” has the meaning set forth in Section 3.1(a). 

“Person” means an individual, corporation, partnership, limited liability company, limited liability partnership, syndicate,
person, trust, association, organization or other entity, including any governmental authority, and including any successor, by merger or otherwise, of any of the foregoing. 

“Public Offering” means an offering of the shares of common stock of the Company pursuant to a registration statement filed
in accordance with the Securities Act. 
 “Registration Rights Agreement” means the Third Amended and Restated Registration
Rights Agreement, to be entered into effective upon the consummation of the IPO, among CII, the Company and the other signatories named therein. 

“Regulatory Entity” means any federal, state, local or foreign court, legislative, executive or regulatory authority or
agency, including (without limitation) any exchange upon which equity securities of the Company are listed. 

“Representatives” means with respect to any Person, any of such Person’s, or its Affiliates’, directors, officers,
employees, general partners, Affiliates, direct or indirect shareholders, members or limited partners, attorneys, accountants, financial and other advisers, and other agents and representatives, including in the case of a Sponsor any Sponsor
Designee designated by it. 

  
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 “Restructuring” means the restructuring of the Company and distribution to the
preferred and common unitholders of CII of shares of common stock of the Company, in accordance with CII’s Fifth Amended and Restated Limited Liability Company Agreement, and the waterfall mechanics contained therein. 

“Securities Act” means the Securities Act of 1933, as amended from time to time, and the rules and regulations promulgated
thereunder. 
 “Share Allocation Notice” has the meaning set forth in Section 3.5(b). 

“Sponsor Designees” has the meaning set forth in Section 2.1(a). 

“Sponsor” means each of Charlesbank Investor and GTCR Investor, and collectively, the “Sponsors.” 

“Subsidiary” means each Person in which a Person owns or controls, directly or indirectly, capital stock or other equity
interests representing more than 50% of the outstanding capital stock or other equity interests, and collectively, “Subsidiaries.” 

“Transfer” means, directly or indirectly, to sell, transfer, assign, pledge, encumber, hypothecate or similarly dispose of,
either voluntarily or involuntarily, by operation of law or otherwise, any Equity Securities owned by a Person or any interest (including but not limited to a beneficial interest) in any Equity Securities owned by a Person. 

“Transferee” means any Person to whom any Participant or any Transferee thereof Transfers Equity Securities of the Company in
accordance with the terms hereof. 
 “Transfer Restriction Period” has the meaning set forth in Section 3.1(a). 

1.2 Terms Generally. The words “hereby,” “herein,” “hereof,” “hereunder” and words of similar
import refer to this Agreement as a whole and not merely to the specific section, paragraph or clause in which such word appears. All references herein to the preamble, recitals, Articles and Sections shall be deemed references to the preamble,
recitals, Articles and Sections of this Agreement unless the context shall otherwise require. The words “include,” “includes” and “including” shall mean “including without limitation.” The definitions given
for terms in this Article I and elsewhere in this Agreement shall apply equally to both the singular and plural forms of the terms defined. Whenever the context may require, any pronoun shall include the corresponding masculine, feminine and
neuter forms. References herein to any agreement or letter shall be deemed references to such agreement or letter as it may be amended, restated or otherwise revised from time to time. 

  
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 ARTICLE II 

SPONSOR DESIGNEES TO THE BOARD 

2.1 Board of Directors. 

(a) Board Designees. Notwithstanding anything to the contrary in this Article II, Charlesbank Investor shall have the right, but
not the obligation, for so long as Charlesbank Investor owns not fewer than          Equity Securities (which such number shall be appropriately adjusted for any combination or consolidation of the Equity
Securities, by reclassification or otherwise, into a greater or lesser number of shares, or any dividend payable in Equity Securities) (the “Minimum Charlesbank Ownership Threshold”), to nominate one designee to serve on the board
of directors of the Company (the “Board”). Notwithstanding anything to the contrary in this Article II, GTCR Investor shall have the right, but not the obligation, for so long as GTCR Investor owns not fewer than
         Equity Securities (which such number shall be appropriately adjusted for any combination or consolidation of the Equity Securities, by reclassification or otherwise, into a greater or lesser number of
shares, or any dividend payable in Equity Securities) (the “Minimum GTCR Ownership Threshold”), to nominate one designee to serve on the Board. To exercise its director designation right, at least 90 days prior to the date of each
meeting of the Company’s stockholders at which directors are to be elected and at which the term of a director designated by a Sponsor will expire, the Sponsor shall recommend to the Nominating Committee a director candidate for nomination
(each, a “Sponsor Designee” and collectively, the “Sponsor Designees”). Each Sponsor Designee recommended pursuant to this Section 2.1(a) shall be an Independent Director and shall be qualified to serve as a
director under the Delaware General Corporation Law (any Sponsor Designee that satisfies such independence and other requirements, an “Eligible Designee”). The Nominating Committee shall evaluate the Sponsor Designees and recommend
their nomination to the Board; provided, however, if the Nominating Committee determines in good faith and consistent with its fiduciary duties that a Sponsor Designee is not an Eligible Designee, the Nominating Committee may, in its
reasonable discretion, reject such Sponsor Designee. In such event, the Charlesbank Investor and/or the GTCR Investor, as the case may be, shall recommend an alternative Sponsor Designee for the Nominating Committee’s evaluation, such process
to continue until a Sponsor Designee is determined to be an Eligible Designee by the Nominating Committee, acting in good faith and consistent with its fiduciary duties. The Board shall approve, upon the recommendation of the Nominating Committee,
the inclusion of the Sponsor Designees for election or reelection, as the case may be, at such meeting in its slate of designees in the proxy materials it distributes to its stockholders, shall recommend that the Company’s stockholders vote in
favor of such Sponsor Designees, shall solicit proxies from the Company’s stockholders for the election of such Sponsor Designees at such meeting, and shall otherwise support such Sponsor Designees for election in a manner consistent with the
manner in which the Company supports its other candidates recommended by the Board for election at such meeting. 
 (b) Replacement of
Directors. No Sponsor Designee may be removed from the Board without cause. If a vacancy is created on the Board as a result of the death, disability, retirement, resignation or removal for cause of any Sponsor Designee, then the Sponsor that
designated such Sponsor Designee shall have the right to designate a replacement to serve in the same class of directors, which replacement shall be evaluated by the Nominating Committee as set forth in Section 2.1(a) and, upon the
recommendation of the Nominating Committee, shall be appointed to fill such vacancy by the Board. In the event that the Charlesbank Investor or the GTCR Investor, as the case may be, shall own less than the Minimum Charlesbank Ownership Threshold or
the Minimum GTCR Ownership Threshold, as applicable, the Sponsor Designee designated by such Sponsor shall offer his or her resignation from the Board. In such event, the Board shall have the discretion, in consideration of a recommendation by the
Nominating Committee, to determine whether to accept or reject such Sponsor Designee’s resignation offer. 

  
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 ARTICLE III 

TRANSFERS / CERTAIN COVENANTS 

3.1 Transfers of Equity Securities. 

(a) Each Participant agrees that, until the date that is 365 calendar days after the consummation of the IPO (the “Transfer Restriction
Period”), such Participant shall not Transfer any of its Equity Securities, except (A) a Transfer that would be permitted by that certain lock-up agreement previously entered into by such Participant and underwriters of the IPO (each,
a “Lock-up Agreement,” and collectively, the “Lock-up Agreements”), without any waiver or other similar action by the underwriters of the IPO, during the period governed by such Lock-up Agreement (as if the Lock-up
Agreement applied during the entire Transfer Restriction Period), as stated therein (the “Lock-up Period”); provided, however, that for purposes of this Section 3.1, the Lock-up Agreements shall be read
without regard to clause (ii) of the second proviso in the second sentence of the second paragraph thereof, which clause restricts certain Transfers except where no filing under Section 16(a) of the Exchange Act shall be required or
voluntarily made, (B) in an underwritten, registered Public Offering, (C) for bona fide hedging purposes not intended to circumvent the restrictions contained in this Section 3 (a “Hedging Transaction”) or
(D) pursuant to the Alternative Transfer Protocol (the “Alternative Transfer Protocol”) set forth in Section 3.5. 

(b) Any Transferee (including any Permitted Transferee) that after the Effective Time acquires Equity Securities from a Participant, other
than in connection with (i) a transfer pursuant to clause (A) of Section 3.1(a) of this Agreement, if the Transferee of such Equity Securities would receive the Equity Securities free from any requirement or obligation to execute a
Lock-up Agreement with the underwriters of the IPO pursuant to the terms of the Lock-up Agreement (as if the Lock-up Agreement applied during the entire Transfer Restriction Period), without any waiver or other similar action by the underwriters of
the IPO, (ii) a Public Offering, (iii) Hedging Transactions or (iv) a transfer pursuant to the Alternative Transfer Protocol, shall, as a condition precedent to the Transfer of such Equity Securities to such Transferee,
(w) become a party to this Agreement by completing and executing a signature page hereto (including the address of such party), (x) represent in writing to the Company that such Transfer was made in accordance with Applicable Law, and
execute all such other agreements or documents as may reasonably be requested by the Company (which may include such other representations and warranties made by the Transferee to the Company as shall be reasonably requested by the Company),
(y) ensure with the transferring stockholders that any regulatory authorizations needed in connection with such Transfer are duly obtained, and (z) deliver such signature page and, if applicable, other agreements and documents to the
Company at its address specified in Section 4.11. Such Person shall, upon its satisfaction of such conditions and acquisition of Equity Securities, be a Participant for all purposes of this Agreement. 

(c) Any Transfer or attempted Transfer of Equity Securities in violation of any provision of this Agreement shall be void, and the Company
shall give no effect thereto. 

  
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 (d) Notwithstanding anything herein to the contrary, if the Transfer restrictions set forth
herein are waived or shortened by the Company for any Participant or any other party bound hereby, the Transfer restrictions set forth in this Article III shall be deemed to be, and hereby are, also waived or shortened for all Participants in the
same manner on a pro rata basis (calculated including the shares held by the Participant or other party bound hereby). 
 3.2 No
Circumvention of Transfer Restrictions. Each Participant agrees that the Transfer restrictions in this Agreement may not be avoided by the holding of Equity Securities directly or indirectly through a Person that was formed solely for purposes
of holding Equity Securities, and undertaking a Transfer of equity securities of such Person, the principal purpose of which is to indirectly dispose of an interest in Common Stock free of such restrictions, if such Transfer results in a substantial
ownership interest or controlling interest (direct or indirect) in the Company being held other than by such Person, whether directly or indirectly. Any Transfer of any Equity Securities, directly or indirectly, of a Person that was formed solely
for purposes of holding shares of Common Stock, the principal purpose of which Transfer was to dispose of (directly or indirectly) the Common Stock held by the Person, that results in a substantial ownership interest or controlling interest (direct
or indirect) in the Company being held other than by such Person, whether directly or indirectly, shall be treated as being a Transfer of the Common Stock held by the applicable Participant in violation of this Agreement. 

3.3 Follow-on Offerings. During the Transfer Restriction Period, each Participant may, in its sole discretion, participate in a
registered offering (“Follow-on Offering”) pursuant to the Registration Rights Agreement, pro rata among the Participants on the basis of the aggregate number of Equity Securities owned by such Participant following the
Restructuring and immediately prior to the IPO. 
 3.4 Legend. 

(a) All certificates and ownership statements representing the Equity Securities held by each Participant shall bear a legend substantially in
the following form: 
 “THE SECURITIES REPRESENTED BY THIS [CERTIFICATE/STATEMENT] ARE SUBJECT TO A STOCKHOLDERS
AGREEMENT (A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY). NO TRANSFER, SALE, ASSIGNMENT, PLEDGE, HYPOTHECATION OR OTHER DISPOSITION OF THE SECURITIES FOR WHICH BOOK ENTRY IS MADE MAY BE MADE EXCEPT IN ACCORDANCE WITH THE PROVISIONS
OF SUCH STOCKHOLDERS AGREEMENT AND (A) PURSUANT TO A REGISTRATION STATEMENT EFFECTIVE UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR (B) PURSUANT TO AN EXEMPTION FROM REGISTRATION THEREUNDER. THE HOLDER OF THIS CERTIFICATE, BY ACCEPTANCE
OF THIS [CERTIFICATE/STATEMENT], AGREES TO BE BOUND BY ALL OF THE PROVISIONS OF SUCH STOCKHOLDERS AGREEMENT.” 
 (b) Upon the permitted
sale of any Equity Securities pursuant to (i) Section 3.1(a)(B), (ii) the Alternative Transfer Protocol under Section 3.5 or (iii) another exemption from 

  
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registration under the Securities Act or upon the termination of this Agreement, the certificates or ownership statements representing such Equity Securities shall be replaced, at the expense of
the Company, with certificates or instruments not bearing the legends required by this Section 3.4; provided that the Company may condition such replacement of certificates or ownership statements under clause (ii) upon the receipt
of an opinion of securities counsel reasonably satisfactory to the Company; provided further that the legend shall be retained in the case of Transfers to a Permitted Transferee as defined in Section 3.1. 

3.5 Alternative Transfer Protocol. In the event that (i) a demand for registration of Equity Securities is properly made under the
Registration Rights Agreement and the Company elects to delay such registered offering pursuant to Section 2.1(a)(ii)(5) or Section 2.1(b)(ii)(5) of the Registration Rights Agreement, (ii) more than 90 calendar days shall have elapsed
after a demand has been properly made under Sections 2.1(a) or 2.1(b) of the Registration Rights Agreement and no closing of such demanded registered offering shall have occurred, or (iii) Participants who are holders of not less than 50% of
the Equity Securities who have notified the Company of their election to participate in any registered offering pursuant to Sections 2.1 or 2.2 of the Registration Rights Agreement (excluding, in the case of an offering pursuant to Section 2.2,
any Equity Securities to be sold by the Company) determine, in their sole discretion, that either the price per Equity Security or the aggregate number of Equity Securities to be offered in connection with such registered offering is not
satisfactory to such Participants, then the transfer of Equity Securities shall be permissible pursuant to the following Alternative Transfer Protocol: 

(a) One or more Participants shall deliver to the Company a notice (the “Alternative Transfer Protocol Notice”) setting forth
a request for transfer of Equity Securities pursuant to the Alternative Transfer Protocol and the circumstances giving rise to the delivery of the Alternative Transfer Protocol Notice. 

(b) Within five calendar days after receiving the Alternative Transfer Protocol Notice, the Company shall provide to all Participants notice
that the Company has received such Alternative Transfer Protocol Notice, together with a spreadsheet setting forth the aggregate number of Equity Securities permitted to be sold pursuant to the Alternative Transfer Protocol and the number of Equity
Securities permitted to be sold by each Participant pursuant to the Alternative Transfer Protocol (the “Share Allocation Notice”). The aggregate number of Equity Securities permitted to be sold pursuant to the Alterative Transfer
Protocol shall be          Equity Securities (the “Aggregate ATP Equity Security Amount”). The maximum number of Equity Securities permitted to be transferred by each Participant pursuant to
the Alterative Transfer Protocol and provided in the Share Allocation Notice shall be determined by allocating the number of Equity Securities equal to the Aggregate ATP Equity Security Amount on a pro rata basis among the Participants based
upon their relative ownership of the Company’s Common Stock immediately following the Restructuring and immediately prior to the IPO (each, a “Participant ATP Equity Security Amount”). 

(c) Each Participant may transfer the number of Equity Securities held by such Participant, in compliance with Applicable Law, up to its
respective Participant ATP Equity Security Amount pursuant to the Alternative Transfer Protocol. 

  
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 ARTICLE IV 

MISCELLANEOUS 
 4.1
Termination. Subject to the early termination of any provision as a result of an amendment to this Agreement agreed to by the Company and the requisite Participants as provided under Section 4.5: 

(a) the provisions of Article II shall, with respect to each Sponsor, terminate as provided in Article II; 

(b) the provisions of Article III shall terminate as of the expiration of the expiration of the Transfer restrictions set forth in
Article III; provided, however, that if any Participant is an employee of the Company or its subsidiaries and such employee experiences an involuntary termination, other than for cause, of his or her employment with the Company or its
subsidiaries during the Transfer Restriction Period, then the provisions of Article III with respect to such employee shall terminate upon the election by such employee to be released from the obligations set forth in Article III; provided,
however, that such release from the obligations set forth in Article III shall not be effective prior to the calendar day immediately following the conclusion of the Lock-up Period; and 

(c) all other provisions of this Agreement shall survive its termination. 

Nothing in this Agreement shall relieve any party from any liability for the breach of any obligations set forth in this Agreement. 

4.2 Effective Time. This Agreement shall be effective as to any specific Participant upon the later of (i) the execution hereof by
the Participants and (ii) the closing of the IPO (the time of such effectiveness, the “Effective Time”); provided, however, that the effectiveness of this Agreement shall be conditioned on the execution hereof prior to
the closing of the IPO by the individuals set forth on Schedule A. 
 4.3 Further Assurances. Each party hereto shall do and
perform or cause to be done and performed all such further acts and things, and shall execute and deliver all such further agreements, certificates, instruments and documents, as any other party hereto reasonably may request in order to carry out
the provisions of this Agreement and the consummation of the transactions contemplated hereby. 
 4.4 No Recourse; No Participant
Duties. The Company and each Participant agrees, notwithstanding anything to the contrary in any other agreement or at law or in equity, that when any Participant takes any action under this Agreement to give or withhold its consent, such
Participant shall have no duty (fiduciary or other) to consider the interests of the Company or the other Participants and may act exclusively in its own interest and shall have no duty to act in good faith; provided that the foregoing shall
in no way affect the obligations of the parties hereto to comply with the provisions of this Agreement. 
 4.5 Amendment; Waivers,
etc. The provisions of Articles I, III and IV of this Agreement may be amended, and the Company and any Participant may take any action herein prohibited, or omit to perform any act herein required to be performed by it, if and only if any

  
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such amendment, action or omission to act, has been approved by holders of a majority of the Equity Securities held by Participants. The provisions of Article II of this Agreement may be amended,
and the Company and any Sponsor may take any action herein prohibited, or omit to perform any act herein required to be performed by it, if and only if any such amendment, action or omission to act, has been approved by the Company, the Charlesbank
Investor and the GTCR Investor; provided that the approval of the Charlesbank Investor and the GTCR Investor shall not be so required with respect to and in order to authorize the amendment, action or omission to act with respect to any
Section of this Agreement for which such Sponsor’s rights or obligations have been terminated pursuant to Section 4.1. Notwithstanding anything herein to the contrary, this Agreement may not be amended in a manner that adversely and
disproportionately affects the rights or obligations of any Participant relative to the rights or obligations of all similarly situated Participants, in each case without the consent of such Participant. The failure of any party to enforce any of
the provisions of this Agreement shall in no way be construed as a waiver of such provisions and shall not affect the right of such party thereafter to enforce each and every provision of this Agreement in accordance with its terms. Any Participant
may waive (in writing) the benefit of any provision of this Agreement with respect to itself for any purpose. Any such waiver shall constitute a waiver only with respect to the specific matter described in such writing and shall in no way impair the
rights of the Participant granting such waiver in any other respect or at any other time. 
 4.6 Assignment. Neither this Agreement
nor any right or obligation arising under this Agreement may be assigned by any party without the prior written consent of the other parties. 

4.7 Binding Effect. This Agreement shall be binding upon and inure to the benefit of the parties hereto and their respective heirs,
successors and permitted assigns. 
 4.8 No Third Party Beneficiaries. Nothing in this Agreement, express or implied, is intended to
or shall confer upon any Person other than the parties and their respective successors and permitted assigns any legal or equitable right, benefit or remedy of any nature under or by reason of this Agreement. 

4.9 Notices. All notices, requests, demands, waivers and other communications required or permitted to be given under this Agreement
shall be in writing and shall be deemed duly given (w) on the date of delivery if delivered personally, (x) on the first Business Day following the date of dispatch if delivered by a nationally recognized next-day courier service,
(y) on the earlier of confirmed receipt or the fifth Business Day following the date of mailing if delivered by registered or certified mail (postage prepaid, return receipt requested) or (z) if sent by facsimile transmission, when
transmitted and receipt is confirmed. All notices hereunder shall be delivered to the addresses set forth below, or pursuant to such other instructions as may be designated in writing by the party to receive such notice: 

(a) if to the Company: 
 Zayo
Group Holdings, Inc. 
 1805 29th Street, Suite 2050 

Boulder, CO 80301 
 Facsimile:

  
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 with a copy (which shall not constitute notice) to: 

Gibson, Dunn & Crutcher LLP 

1801 California Street, Suite 4200 

Denver, CO 80202 
 Attention:
Robyn E. Zolman, Esq. 
 Facsimile: (303) 313-2830 

(b) if to the Charlesbank Investor: 

Charlesbank Capital Partners LLC 
  

Attention:      

Facsimile:      

with a copy (which shall not constitute notice) to: 
  

 
  

Attention:      

Facsimile:      

(c) if to the GTCR Investor, to: 

GTCR LLC 
  

Attention:      

Facsimile:      

with a copy (which shall not constitute notice) to: 
  

 
  

Attention:      

Facsimile:      

(d) if to any other Participant, to its address specified on Schedule A or Schedule B, as the case may be. 

4.10 Severability. Any term or provision of this Agreement that is invalid, illegal or unenforceable in any jurisdiction shall, as to
that jurisdiction, be ineffective to the extent of such invalidity, illegality or unenforceability without rendering invalid, illegal or unenforceable the 

  
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remaining terms and provisions of this Agreement or affecting the validity, illegality or enforceability of any of the terms or provisions of this Agreement in any other jurisdiction. If any
provision of this Agreement is so broad as to be unenforceable, the provision shall be interpreted to be only so broad as is enforceable. Upon such determination that any term or other provision is invalid, illegal or incapable of being enforced,
the parties hereto shall negotiate in good faith to modify this Agreement so as to effect the original intent of the parties as closely as possible in a mutually acceptable manner in order that the transactions contemplated herein are consummated as
originally contemplated to the fullest extent possible. 
 4.11 Headings. The headings contained in this Agreement are for purposes
of convenience only and shall not affect the meaning or interpretation of this Agreement. 
 4.12 Entire Agreement. This Agreement
constitutes the entire agreement and supersedes all prior agreements and understandings, both written and oral, among the parties with respect to the subject matter hereof. 

4.13 Governing Law. This Agreement will be governed by and construed in accordance with the laws of the State of Delaware (regardless
of the laws that might otherwise govern under applicable principles or rules of conflicts of law to the extent such principles or rules are not mandatorily applicable by statute and would require the application of the laws of another jurisdiction).

 4.14 Consent to Jurisdiction. Each of the parties irrevocably agrees that any legal action or proceeding arising out of or
relating to this Agreement brought by any party or its Affiliates against any other party or its Affiliates shall be brought and determined in the Court of Chancery of the State of Delaware; provided, that if jurisdiction is not then
available in the Court of Chancery of the State of Delaware, then any such legal action or proceeding may be brought in any federal court located in the State of Delaware or any other Delaware state court. Each of the parties hereby irrevocably
submits to the jurisdiction of the aforesaid courts for itself and with respect to its property, generally and unconditionally, with regard to any such action or proceeding arising out of or relating to this Agreement and the transactions
contemplated hereby. Each of the parties agrees not to commence any action, suit or proceeding relating thereto except in the courts described above in Delaware, other than actions in any court of competent jurisdiction to enforce any judgment,
decree or award rendered by any such court in Delaware as described herein. Each of the parties further agrees that notice as provided herein shall constitute sufficient service of process and the parties further waive any argument that such service
is insufficient. Each of the parties hereby irrevocably and unconditionally waives, and agrees not to assert, by way of motion or as a defense, counterclaim or otherwise, in any action or proceeding arising out of or relating to this Agreement or
the transactions contemplated hereby, (a) any claim that it is not personally subject to the jurisdiction of the courts in Delaware as described herein for any reason, (b) that it or its property is exempt or immune from jurisdiction of
any such court or from any legal process commenced in such courts (whether through service of notice, attachment prior to judgment, attachment in aid of execution of judgment, execution of judgment or otherwise) and (c) that (i) the suit,
action or proceeding in any such court is brought in an inconvenient forum, (ii) the venue of such suit, action or proceeding is improper or (iii) this Agreement, or the subject matter hereof, may not be enforced in or by such courts. 

  
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 4.15 Waiver of Jury Trial. EACH OF THE PARTIES TO THIS AGREEMENT HEREBY IRREVOCABLY WAIVES
ALL RIGHT TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY. 

4.16 Enforcement. Each party hereto acknowledges that money damages would not be an adequate remedy in the event that any of the
covenants or agreements in this Agreement are not performed in accordance with its terms, and it is therefore agreed that in addition to and without limiting any other remedy or right it may have, the non-breaching party will have the right to an
injunction, temporary restraining order or other equitable relief in any court of competent jurisdiction enjoining any such breach and enforcing specifically the terms and provisions hereof. In the event that the Company or one or more Participants
shall file suit to enforce the covenants contained in this Agreement (or obtain any other remedy in respect of any breach thereof), the prevailing party in the suit shall be entitled to recover, in addition to all other damages to which it may be
entitled, the costs incurred by such party in conducting the suit, including, without limitation, reasonable attorney’s fees and expenses. 

4.17 Counterparts; Facsimile Signatures. This Agreement may be executed in any number of counterparts, each of which shall be an
original, but all of which together shall constitute one instrument. This Agreement may be executed by facsimile signature(s). 

[Signature Page Follows.] 

  
 13 

 IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement by their authorized
representatives as of the date first above written. 
  

			
	ZAYO GROUP HOLDINGS, INC.
		
	By:	 	  

	Name:	 	
	Title:	 	
	
	CHARLESBANK CAPITAL PARTNERS LLC
		
	By:	 	
	Its:	 	Manager
		
	By:	 	  

	Name:	 	
	Title:	 	
	
	GTCR LLC
		
	By:	 	
	Its:	 	Manager
		
	By:	 	  

	Name:	 	
	Title:	 	

 [Signature Page to Stockholders Agreement] 

 
			
	PARTICIPANT
	
	  

		
	By:	 	  

	Name:	 	
	Title:	 	
	
	Address:
	
	  

	
	  

	
	  

 [Signature Page to Stockholders Agreement] 

 SCHEDULE A 

Dan Caruso, Bear Equity, LLC, Bear Investments, LLLP, and VP Holdings, LLC 

Ken desGarennes, Tablerock Investments, LLC and Tablerock Investments II, LLC 

John Scarano, ESU Investments, LLC and Scarano 2014 GRAT #1 
 Matt
Erickson and MRE 2014 GRAT 
 Chris Morley and Mango 2014 Grantor Retained Annuity Trust and Mango Holdings, LLC 

David Howson and BON Famille 2014 Irrevocable Trust 
 Glenn Russo
and GSR 2014 GRAT 
 Sandi Mays 
 Chris Murphy and Christopher
G. Murphy 2014 Grantor Retained Annuity Trust 
 Jason Tibbs 

James Nolte 
 Scott Beer 

Tim Gentry 
 Greg Hadlock 

Fritz Hendricks 
 Gillis Cashman 

Stephanie Copeland 
 Stephanie Comfort 

Rick Connor 
 Don Gips 

Linda Rottenberg 
 The address for each of the Participants set
forth above is: 
 [Participant] 

c/o Zayo Group Holdings, Inc. 

1805 29th Street, Suite 2050 

Boulder, CO 80301 
 Facsimile:
[    ] 
 with a copy (which shall not constitute notice) to: 

Gibson, Dunn & Crutcher LLP 

1801 California Street, Suite 4200 

Denver, CO 80202 
 Attention:
Robyn E. Zolman, Esq. 
 Facsimile: (303) 313-2830 

 SCHEDULE BEX-10.19

 Exhibit 10.19 

FIRST AMENDMENT TO EMPLOYMENT AGREEMENT 

This First Amendment to Employment Agreement (the “Amendment”) is entered into as of October 2, 2014 between Communications
Infrastructure Investments, LLC, a Delaware limited liability company (“CII”) and Zayo Group Holdings, Inc., a Delaware corporation, (“Zayo” and collectively with CII, the “Company”) and Daniel P.
Caruso (the “Executive”) (each of the foregoing individually a “Party” and collectively the “Parties”). 

WHEREAS, the Parties wish to amend the Executive’s Employment Agreement dated February 15, 2014
(“Agreement”) consistent with the terms contained herein. The Company’s Compensation Committee has reviewed and approved the terms and conditions contained herein. 

1. Cash Compensation. 
 Cash
Compensation. Contingent upon the completion of the Company’s IPO, and effective November 1, 2014, the Executive’s base salary shall be changed from a rate of $400,000.00 per annum to a rate of $17,500.00 per annum, which shall be
paid in accordance with the customary payroll practices of the Company (the “Base Salary”). 
 2. Equity Compensation Awards. 

Grant of Restricted Stock Units (“RSUs”). Contingent upon the completion of the Company’s IPO, and effective
November 1, 2014, the Company shall grant to Executive a quantity of RSUs that equates to an aggregate value of $2,750,000.00 on the terms and conditions set forth in this Amendment, the Executive’s Employment Agreement dated
February 15, 2014, and consistent with the Company’s Part A RSU program. Such RSUs shall be subject to a four (4) quarter vesting term and shall vest on December 31, 2015 (provided the subject IPO occurs on or before
December 31, 2014). 
  

			
	Executive
		
	By:	 	 /s/ Daniel P. Caruso

		 	Daniel P. Caruso
		
	By:	 	 /s/ Ken desGarennes

	Name:	 	Ken desGarennes
	Title:	 	Chief Financial Officer

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