SUBSIDIARY GUARANTY AGREEMENT

Exhibit 10.21

SUBSIDIARY GUARANTY AGREEMENT

Dated as of January 30, 2008

from

THE SUBSIDIARY GUARANTORS NAMED HEREIN

for the benefit of

THE HOLDERS OF THE NOTES

RE:

$60,000,000 7.17% SENIOR NOTES DUE JANUARY 30, 2013

OF

GFI GROUP INC.

TABLE OF CONTENTS

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THIS SUBSIDIARY GUARANTY AGREEMENT, dated as of January 30, 2008 (the “Guaranty” ), from each of:

for the benefit of the holders from time to time of the Notes (as defined below) (the “Holders” ).  Capitalized terms used herein are defined in Section 14 hereof or the Note Purchase Agreement referred to below.

WHEREAS, GFI Group Inc., a Delaware corporation (the “Company” ) will authorize the issue and sale of $60,000,000 7.17% Senior Notes due January 30, 2013 (the “Notes” ) pursuant to a Note Purchase Agreement, dated as of the date hereof (as amended, modified or supplemented from time to time, the “Note Purchase Agreement” ) among the Company and the purchasers named therein.

WHEREAS, each of the Subsidiary Guarantors is a Subsidiary of the Company.

WHEREAS, the Company has agreed that certain of its Subsidiaries will guarantee the Company’s obligations under and in accordance with the Notes, the Note Purchase Agreement and the Collateral Documents.

WHEREAS, the Subsidiary Guarantors each acknowledge that it will derive substantial benefits from the issuance of the Notes and the execution and delivery of each Note Document.

NOW, THEREFORE, in consideration of the premises and to induce the Holders to purchase the Notes, each of the Subsidiary Guarantors, intending to be legally bound, hereby agrees for the benefit of the Holders, as follows:

SECTION 1.                                                  GUARANTY.

Each Subsidiary Guarantor with all other Subsidiary Guarantors, hereby absolutely, unconditionally and irrevocably guarantees, jointly and severally, as a primary obligor and not merely as a surety, to each Holder and its successors and assigns, the full and punctual payment and performance when due, whether at stated maturity, by acceleration or otherwise, of the principal of and Make-Whole Amount (if any), and interest on (including, without limitation, interest, whether or not an allowable claim, accruing after the date of filing of any petition in

bankruptcy, or the commencement of any bankruptcy, insolvency or similar proceeding relating to the Company) the Notes and all other amounts payable by the Company under the Note Documents and all other obligations, agreements and covenants of the Company now or hereafter existing under the Note Documents whether for principal, Make-Whole Amount, interest (including interest accruing or becoming owing both prior to and subsequent to the commencement of any proceeding against or with respect to the Company under any chapter of the Bankruptcy Code), indemnification payments, expenses (including reasonable attorneys’ fees and expenses) or otherwise, and all reasonable costs and expenses, if any, incurred by any Holder in connection with enforcing any rights under the Note Documents to which the Subsidiary Guarantors are a party (all such obligations being the “Guaranteed Obligations” ), and agrees to pay any and all reasonable expenses incurred by each Holder in enforcing this Guaranty; provided that, notwithstanding anything contained herein and in the Note Documents to the contrary, the maximum liability of each Subsidiary Guarantor hereunder and under the Note Documents shall in no event exceed such Guarantor’s Maximum Guaranteed Amount, and provided further, each Subsidiary Guarantor shall be unconditionally required to pay all amounts demanded of it hereunder prior to any determination of such Maximum Guaranteed Amount and the recipient of such payment, if so required by a final non-appealable order of a court of competent jurisdiction, shall then be liable for the refund of any excess amounts.  If any such rebate or refund is ever required, all other Subsidiary Guarantors (and the Company) shall be fully liable for the repayment thereof to the maximum extent allowed by applicable law.  This Guaranty is an absolute, unconditional, present and continuing guaranty of payment and not of collectibility and is in no way conditioned upon any attempt to collect from the Company or any other action, occurrence or circumstance whatsoever.  Each Subsidiary Guarantor agrees that the Guaranteed Obligations may at any time and from to time exceed the Maximum Guaranteed Amount of such Subsidiary Guarantor without impairing this Guaranty or affecting the rights and remedies of the Holders hereunder.

Notwithstanding any stay, injunction or other prohibition preventing such action against the Company, if for any reason whatsoever the Company shall fail or be unable duly, punctually and fully to perform and (in the case of the payment of Guaranteed Obligations) pay such amounts as and when the same shall become due and (in the case of the payment of Guaranteed Obligations) payable or to perform or comply with any other Guaranteed Obligation, whether or not such failure or inability shall constitute an “Event of Default” under the Note Documents, each Subsidiary Guarantor will forthwith (in the case of the payment of Guaranteed Obligations) pay or cause to be paid such amounts to the Holders, in lawful money of the United States of America, at the place specified in the Note Purchase Agreement, or perform or comply with such Guaranteed Obligations or cause such Guaranteed Obligations to be performed or complied with, (in the case of the payment of Guaranteed Obligations) together with interest (in the amounts and to the extent required under the relevant Notes) on any amount due and owing.

SECTION 2.                                                  REPRESENTATIONS AND WARRANTIES.

Each Subsidiary Guarantor hereby represents and warrants as follows:

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(a)       All representations and warranties contained in the Note Documents that relate to such Subsidiary Guarantor are true and correct in all respects and are incorporated by reference with the same force and effect as though set forth herein in full.

(b)       Such Subsidiary Guarantor acknowledges that any default in the due observance or performance by such Subsidiary Guarantor of any covenant, condition or agreement contained herein or in any Collateral Document to which it is a party (if, after the running of any applicable notice and opportunity to cure periods provided in the Note Purchase Agreement, such default or event of default remains uncured) shall constitute an Event of Default.

(c)       There are no conditions precedent to the effectiveness of this Guaranty or any other Note Document to which it is a party that have not been satisfied or expressly waived.

(d)       Such Subsidiary Guarantor has, independently and without reliance upon the Holders and based on such documents and information as it has deemed appropriate, made its own credit analysis and decision to enter into this Guaranty and any other Note Document to which it is a party.  Such Subsidiary Guarantor has investigated fully the benefits and advantages which will be derived by it from execution of this Guaranty and any other Note Document to which it is a party as a condition precedent to the issue, sale and purchase of the Notes by the Holders, and the Board of Directors/Managers of such Subsidiary Guarantor has decided that a direct and/or an indirect benefit will accrue to such Subsidiary Guarantor by reason of the execution of this Guaranty and any other Note Document to which it is a party as a condition precedent to the issue, sale and purchase of the Notes by the Holders.

(e)       (i) This Guaranty is not given with actual intent to hinder, delay or defraud any Person to which such Subsidiary Guarantor is or will become, on or after the date hereof, indebted; (ii) such Subsidiary Guarantor has received consideration in exchange for the giving of this Guaranty; (iii) such Subsidiary Guarantor is not insolvent on the date hereof and will not become insolvent as a result of the giving of this Guaranty; (iv) such Subsidiary Guarantor is not engaged in a business or transaction, nor is about to engage in a business or transaction, for which any property remaining with such Subsidiary Guarantor constitutes an unreasonably small amount of capital; and (v) such Subsidiary Guarantor does not intend to incur debts that will be beyond such Subsidiary Guarantor’s ability to pay as such debts mature.

(f)        Such Subsidiary Guarantor is a corporation or other legal entity duly organized and validly existing under the laws of its state of organization, and has the requisite power, authority and legal right under the laws of its state of organization to conduct its business as presently conducted and to execute, deliver and perform its obligations under this Guaranty.

(g)       The execution, delivery and performance of this Guaranty have been duly authorized by all necessary corporate action on the part of such Subsidiary Guarantor, and does not require any consent or approval of, or the giving of notice to, or the taking of any other action in respect of, any stockholder or trustee or holder of any indebtedness or obligations of such Subsidiary Guarantor except to the extent it has been previously obtained.  This Guaranty constitutes a legal, valid and binding obligation of such Subsidiary Guarantor, enforceable against such Subsidiary Guarantor in accordance with its terms, except that such enforceability is

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subject to any limitations arising from bankruptcy, insolvency, liquidation, moratorium, reorganization and other similar laws of general application relating to or affecting the rights of creditors or pledgees and to general principles of equity (regardless of whether such enforceability is considered in a proceeding in equity or at law).

(h)       The execution, delivery and performance of this Guaranty do not and will not conflict with or result in any violation of or default under any provision of the Articles of Incorporation or by-laws or partnership agreement, as the case may be, of such Subsidiary Guarantor, or any indenture, mortgage, deed of trust, instrument, law, rule or regulation binding on such Subsidiary Guarantor or to which such Subsidiary Guarantor is a party.

(i)        The execution, delivery and performance of this Guaranty do not and will not result in violation of any judgment or order applicable to such Subsidiary Guarantor or result in the creation or imposition of any Lien on any of the properties or revenues of such Subsidiary Guarantor pursuant to any requirement of law or any indenture, mortgage, deed of trust or other instrument to which such Subsidiary Guarantor is a party.

(j)        The execution, delivery and performance of this Guaranty do not and will not conflict with and do not and will not require any consent, approval or authorization of, or registration or filing with, any governmental authority or agency of the state of organization of such Subsidiary Guarantor or of the United States or any State.

(k)       There are no pending or, to the knowledge of such Subsidiary Guarantor, threatened actions or proceedings against or affecting such Subsidiary Guarantor or any of its properties by or before any court or administrative agency or arbiter that would adversely affect the ability of such Subsidiary Guarantor to perform its obligations hereunder or call into question the validity or enforceability of this Guaranty.

(l)        Such Subsidiary Guarantor’s obligations under this Guaranty are at least pari passu in right of payment with all other Senior Secured Indebtedness (actual or contingent).

(m)      No Subsidiary Guarantor is in breach of or default under or with respect to any instrument, document or agreement binding upon such Subsidiary Guarantor which breach or default is reasonably probable to have a Material Adverse Effect or result in the creation of a Lien on any property of such Subsidiary Guarantor other than Liens permitted under Section 10.5 of the Note Purchase Agreement.  Such Subsidiary Guarantor is in compliance with all applicable requirements of law except such non-compliance as would not have a Material Adverse Effect.

(n)       The execution, delivery and performance by each Subsidiary Guarantor of this Guaranty will not render such Subsidiary Guarantor insolvent, nor is it being made in contemplation of such Subsidiary Guarantor’s insolvency, and such Subsidiary Guarantor does not have unreasonably small capital.

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SECTION 3.                                                  SUBSIDIARY GUARANTOR’S OBLIGATIONS UNCONDITIONAL.

(a)           This Guaranty shall constitute a guarantee of payment, performance and compliance and not of collection, and each Subsidiary Guarantor specifically agrees that it shall not be necessary, and that such Subsidiary Guarantor shall not be entitled to require, before or as a condition of enforcing the liability of such Subsidiary Guarantor under this Guaranty or requiring payment or performance of the Guaranteed Obligations by any Subsidiary Guarantor hereunder, or at any time thereafter, that any Holder:  (a) file suit or proceed to obtain or assert a claim for personal judgment against the Company or any other Person that may be liable for or with respect to any Guaranteed Obligation; (b) make any other effort to obtain payment or performance of any Guaranteed Obligation from the Company or any other Person that may be liable for or with respect to such Guaranteed Obligation, except for the making of the demands, when appropriate, described in Section 1; (c) foreclose against, or seek to realize upon security now or hereafter existing for such Guaranteed Obligations; (d) except to the extent set forth in Section 1, exercise or assert any other right or remedy to which such Holder is or may be entitled in connection with any Guaranteed Obligation or any security or other guaranty therefor; or (e) assert or file any claim against the assets of the Company or any other Person liable for any Guaranteed Obligation.  Each Subsidiary Guarantor agrees that this Guaranty shall be continuing, and that the Guaranteed Obligations will be paid and performed in accordance with their terms and the terms of this Guaranty, and are the primary, absolute and unconditional obligations of such Subsidiary Guarantor, irrespective (to the extent permitted by applicable law) of the value, genuineness, validity, legality, regularity or enforceability or lack thereof of any part of the Guaranteed Obligations or any agreement or instrument relating to the Guaranteed Obligations or this Guaranty, or the existence of any indemnities with respect to the existence of any other guarantee of or security for any of the Guaranteed Obligations, or any substitution, release or exchange of any other guarantee of or security for any of the Guaranteed Obligations, and, to the fullest extent permitted by applicable law, irrespective of any other circumstance whatsoever that might otherwise constitute a legal or equitable discharge or defense of a surety or guarantor, it being the intent of this Section 3 that the obligations of each Subsidiary Guarantor hereunder shall be irrevocable, primary, absolute and unconditional under any and all circumstances.

(b)           Each Subsidiary Guarantor hereby expressly waives notice of acceptance of and reliance upon this Guaranty, diligence, presentment, demand of payment or performance, protest and all other notices (except as otherwise provided for in Section 1) whatsoever, any requirement that the Holders exhaust any right, power or remedy or proceed against the Company or against any other Person under any other guarantee of, or security for, or any other agreement, regarding any of the Guaranteed Obligations.  Each Subsidiary Guarantor further agrees that, subject solely to the requirement of making demands under Section 1, the occurrence of any event or other circumstance that might otherwise vary the risk of the Company or such Subsidiary Guarantor or constitute a defense (legal or equitable) available to, or a discharge of, or a counterclaim or right of set-off by, the Company or such Subsidiary Guarantor (other than the full and indefeasible due payment and performance of the Guaranteed Obligations), shall not affect the liability of such Subsidiary Guarantor hereunder.

(c)           The obligations of each Subsidiary Guarantor under this Guaranty are not subject to any counterclaim, set-off, deduction, diminution, abatement, recoupment, suspension,

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deferment or defense based upon any claim such Subsidiary Guarantor or any other Person may have against the Company, any Holder or any other Person, and (to the extent permitted by applicable law) shall remain in full force and effect without regard to, and shall not be released, discharged or in any way affected by, any circumstances or condition whatsoever (whether or not such Subsidiary Guarantor or the Company shall have any knowledge or notice thereof), including:

(i)            any renewal, extension, modification, increase, decrease, alteration or rearrangement of all or any part of the Guaranteed Obligations or any instrument executed in connection therewith, or any contract or understanding with the Company, the Holders, or any of them, or any other Person, pertaining to the Guaranteed Obligations;

(ii)           any adjustment, indulgence, forbearance or compromise that might be granted or given by any Holder to the Company or any other Person liable on the Guaranteed Obligations, or the failure of any Holder to assert any claim or demand or to exercise any right or remedy against the Company or any other Person under the provisions of the Note Documents or otherwise; or any rescission, waiver, amendment or modification of, or any release from any of the terms or provisions of, the Note Documents, any guarantee or any other agreement;

(iii)          the insolvency, bankrptcy arangement, adjustment, composition, liquidation, disability, dissolution or lack of power of the Company or any other Person at any time liable for the payment of all or part of the Guaranteed Obligations; or any change, restructuring or termination of the existence of the Company or any other such Person, or any sale, lease or transfer of any or all of the assets of the Company or any other such Person, or any change in the shareholders, partners, or members of the Company or any other such Person; or any default, failure or delay, willful or otherwise, in the performance of the Guaranteed Obligations;

(iv)         the invalidity, illegality or unenforceability of all or any part of the Guaranteed Obligations, or any document or agreement executed in connection with the Guaranteed Obligations, for any reason whatsoever, including the fact that the Guaranteed Obligations, or any part thereof, exceed the amount permitted by law, the act of creating the Guaranteed Obligations or any part is ultra vires, the officers or representatives executing the documents or otherwise creating the Guaranteed Obligations acted in excess of their authority, the Guaranteed Obligations violate applicable usury laws, the Company or any other Person has valid defenses, claims or offsets (whether at law, in equity or by agreement) which render the Guaranteed Obligations wholly or partially uncollectible from the Company or any other Person, the creation, performance or repayment of the Guaranteed Obligations (or the execution, delivery and performance of any document or instrument representing part of the Guaranteed Obligations or executed in connection with the Guaranteed Obligations or given to secure the repayment of the Guaranteed Obligations) is illegal, uncollectible, legally impossible or unenforceable, or the documents or instruments pertaining to the Guaranteed Obligations have been forged or otherwise are irregular or not genuine or authentic;

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(v)          any full or partial release of the liability of the Company on the Guaranteed Obligations or any part thereof, of any co-guarantors, or of any other Person now or hereafter liable, whether directly or indirectly, jointly, severally, or jointly and severally, to pay, perform, guarantee or assure the payment of the Guaranteed Obligations or any part thereof, it being recognized, acknowledged and agreed by each Subsidiary Guarantor that such Subsidiary Guarantor may be required to pay the Guaranteed Obligations in full without assistance or support of any other Person, and such Subsidiary Guarantor has not been induced to enter into this Guaranty on the basis of a contemplation, belief, understanding or agreement that any parties other than the Company will be liable to perform the Guaranteed Obligations, or that the Holders will look to other parties to perform the Guaranteed Obligations;

(vi)         the taking or accepting of any other security, collateral or guaranty, or other assurance of payment, for all or any part of the Guaranteed Obligations;

(vii)       any release, surrender, exchange, subordination, deterioration, waste, loss or impairment (including negligent, unreasonable or unjustifiable impairment) of any collateral, property or security, at any time existing in connection with, or assuring or securing payment of, all or any part of the Guaranteed Obligations;

(viii)       the failure of any Holder or any other Person to exercise diligence or reasonable care in the preservation, protection, enforcement, sale or other handling or treatment of all or any part of such collateral, property or security;

(ix)          the fact that any collateral, security, security interest or lien contemplated or intended to be given, created or granted as security for the repayment of the Guaranteed Obligations shall not be properly perfected or created, or shall prove to be unenforceable or subordinate to any other security interest or lien, it being recognized and agreed by each Subsidiary Guarantor that such Subsidiary Guarantor is not entering into this Guaranty in reliance on, or in contemplation of the benefits of, the validity, enforceability, collectibility or value of any of the collateral;

(x)           any payment by the Company to any Holder being held to constitute a preference under any Fraudulent Conveyance Law, or for any reason any Holder being required to refund such payment or pay such amount to the Company or someone else;

(xi)          any other action taken or omitted to be taken with respect to the Guaranteed Obligations, or the security and collateral therefor, whether or not such action or omission prejudices such Subsidiary Guarantor or increases the likelihood that such Subsidiary Guarantor will be required to pay the Guaranteed Obligations pursuant to the terms hereof, it being the unambiguous and unequivocal intention of such Subsidiary Guarantor that it shall be obligated to pay the Guaranteed Obligations when due, notwithstanding any occurrence, circumstance, event, action or omission whatsoever, whether or not contemplated, and whether or not otherwise or particularly described herein, except for the full and final payment and satisfaction of the Guaranteed Obligations in cash;

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(xii)         the fact that all or any of the Guaranteed Obligations cease to exist by operation of law, including by way of a discharge, limitation or tolling thereof under applicable bankruptcy laws;

(xiii)        any other circumstance (including any statute of limitations) that might in any manner or to any extent otherwise constitute a defense available to, vary the risk of, or operate as a discharge of, the Company or any Person as a matter of law or equity;

(xiv)        any merger or consolidation of the Company or any Subsidiary Guarantor into or with any other Person or any sale, lease or transfer of any of the assets of the Company to any other Person;

(xv)         any change in the ownership of any shares of c