Exhibit 4.3

        Unless this Security is presented by an authorized representative of The Depository Trust Company, a New York corporation ("DTC"), 55 Water Street, New York, New York, to the Issuer (as defined below) or its agent for registration of transfer, exchange or payment, and any certificate issued is registered in the name of Cede & Co. or in such other name as is requested by an authorized representative of DTC (and any payment is made to Cede & Co. or to such other entity as is requested by an authorized representative of DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner hereof, Cede & Co., has an interest herein.

        This Security is a Global Security within the meaning set forth in the Indenture hereinafter referred to and is registered in the name of DTC or a nominee of DTC. This Security is exchangeable for Securities registered in the name of a person other than DTC or its nominee only in the limited circumstances described in the Indenture, and may not be transferred except as a whole by DTC to a nominee of DTC or another nominee of DTC or by DTC or its nominee to a successor Depository or its nominee.

MACK-CALI REALTY, L.P.

6.15% NOTE DUE 2012

        MACK-CALI REALTY, L.P., a limited partnership duly organized and existing under the laws of the State of Delaware (herein referred to as the "Issuer" which term shall include any Successor Person under the Indenture hereinafter referred to), for value received, hereby promises to pay to CEDE & CO., or registered assigns, upon presentation, the principal sum of NINETY-FOUR MILLION NINE HUNDRED AND FOURTEEN THOUSAND AND 00/100 DOLLARS on December 15, 2012, and to pay interest on the outstanding principal amount thereon from December 20, 2002, or from the immediately preceding Interest Payment Date to which interest has been paid or duly provided for, semi-annually in arrears on June 15 and December 15 in each year, commencing June 15, 2003, at the rate of 6.15% per annum, until the entire principal hereof is paid or made available for payment. The interest so payable and punctually paid or duly provided for on any Interest Payment Date will, as provided in the Indenture, be paid to the Person in whose name this Security is registered at the close of business on the Regular Record Date for such interest which shall be the June 1 or December 1 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Any such interest not so punctually paid or duly provided for shall forthwith cease to be payable to the Holder on such Regular Record Date, and may either be paid to the Person in whose name this Security is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of the Securities not more than 15 days and not less than 10 days prior to such Special Record Date, or may be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities may be listed, and upon such notice as may be required by such exchange, all as more fully provided in the Indenture. Payment of the principal of and interest on this Security will be made at the office or agency maintained for that purpose in the City of Wilmington, Delaware or elsewhere as provided in the Indenture, in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts; provided, however, that at the option of the Issuer payments of principal and interest on the Notes (other than payments of principal and interest due at Maturity) may be made (i) by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register or (ii) by wire transfer to an account of the Person entitled thereto located within the United States.

1

        Securities of this series are one of a duly authorized issue of securities of the Issuer (herein called the "Securities"), issued and to be issued in one or more series under an Indenture, dated as of March 16, 1999, among the Issuer, Mack-Cali Realty Corporation and Wilmington Trust Company, (herein called the "Trustee", which term includes any successor trustee under the Indenture), as supplemented by Supplemental Indenture No. 1, dated as of March 16, 1999, as further supplemented by Supplemental Indenture No. 2, dated as of August 2, 1999, as further supplemented by Supplemental Indenture No. 3, dated as of December 21, 2000, as further supplemented by Supplemental Indenture No. 4, dated as of January 29, 2001, and as further supplemented by Supplemental Indenture No. 5, dated as of December 20, 2002 (as so supplemented, herein called the "Indenture"), between the Issuer and the Trustee to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Issuer, the Trustee and the Holders of the Securities and of the terms upon which the Securities are authenticated and delivered. This Security is one of the series designated in the first page thereof, limited in aggregate principal amount to $94,914,000, except as the aggregate principal amount may be increased pursuant to Section 2.2 of Supplemental Indenture No. 5 referred to above.

        Securities of this series may be redeemed at any time at the option of the Issuer, in whole or in part, upon notice of not more than 60 nor less than 30 days prior to the Redemption Date, at a redemption price equal to the sum of (i) the principal amount of the Securities being redeemed plus accrued and unpaid interest thereon up to but not including the Redemption Date and (ii) the Make-Whole Premium, if any, with respect to such Securities.

        The Indenture contains provisions for defeasance at any time of (a) the entire indebtedness of the Issuer on this Security and (b) certain restrictive covenants and the related defaults and Events of Default applicable to the Issuer, in each case, upon compliance by the Issuer with certain conditions set forth in the Indenture, which provisions apply to this Security.

        If an Event of Default with respect to the Securities shall occur and be continuing, the principal of the Securities may be declared due and payable in the manner and with the effect provided in the Indenture.

        As provided in and subject to the provisions of the Indenture, the Holder of this Security shall not have the right to institute any proceeding with respect to the Indenture or for the appointment of a receiver or trustee or for any other remedy thereunder, unless such Holder shall have previously given written notice to the Trustee of a continuing Event of Default with respect to the Securities, the Holders of not less than a majority in principal amount of the Securities of this series at the time Outstanding shall have made written request to the Trustee to institute proceedings in respect of such Event of Default as Trustee and offered the Trustee reasonable indemnity and the Trustee shall not have received from the Holders of a majority in principal amount of Securities of this series at the time Outstanding a direction inconsistent with such request, and shall have failed to institute any such proceeding, for 60 days after receipt of such notice, request and offer of indemnity. The foregoing shall not apply to any suit instituted by the Holder of this Security for the enforcement of any payment of principal hereof or any interest on or after the respective due dates expressed herein.

        The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Issuer and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Issuer and the Trustee with the consent of the Holders of not less than a majority in principal amount of the Outstanding Securities of each series of Securities then Outstanding affected thereby. The Indenture also contains provisions permitting the Holders of specified percentages in principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Issuer with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be

2

conclusive and binding upon such Holder and upon all future Holders of this Security and of any Security issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security.

        No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Issuer, which is absolute and unconditional, to pay the principal of (and Make-Whole Premium, if any) and interest on this Security at the times, place and rate, and in the coin or currency, herein prescribed.

        As provided in the Indenture and subject to certain limitations therein set forth, the transfer of this Security is registrable in the Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Issuer in any Place of Payment where the principal of (and Make-Whole Premium, if any) and interest on this Security are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Issuer and the Security Registrar duly executed by the Holder hereof or his attorney duly authorized in writing, and thereupon one or more new Securities of this series, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees.

        Except as set forth in Section 302 of the Indenture, the Securities of this series are issuable only in registered form without coupons in denominations of $1,000 and any integral multiple thereof. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series of a different authorized denomination, as requested by the Holder surrendering the same.

        No service charge shall be made for any such registration of transfer or exchange, but the Issuer may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith.

        Prior to due presentment of this Security for registration of transfer, the Issuer, the Trustee and any agent of the Issuer or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security be overdue, and neither the Issuer, the Trustee nor any such agent shall be affected by notice to the contrary.

        No recourse under or upon any obligation, covenant or agreement contained in the Indenture or in this Security, or because of any indebtedness evidenced hereby or thereby, shall be had against any promoter, as such, or against any past, present or future shareholder, officer or director, as such, of the Issuer or of any successor, either directly or through the Issuer or any successor, under any rule of law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise, all such liability being expressly waived and released by the acceptance of this Security by the Holder thereof and as part of the consideration for the issue of the Securities of this series.

        All capitalized terms used in this Security which are defined in the Indenture shall have the meanings assigned to them in the Indenture.

        THE INDENTURE AND THE SECURITIES, INCLUDING THIS SECURITY, SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

        Pursuant to a recommendation promulgated by the Committee on Uniform Security Identification Procedures, the Issuer has caused "CUSIP" numbers to be printed on the Securities of this series as a convenience to the Holders of such Securities. No representation is made as to the correctness or accuracy of such CUSIP numbers as printed on the Securities, and reliance may be placed only on the other identification numbers printed hereon.

        Unless the certificate of authentication hereon has been executed by or on behalf of the Trustee by manual signature, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose.

        [REMAINDER OF PAGE INTENTIONALLY BLANK; SIGNATURE PAGE FOLLOWS]

3

        IN WITNESS WHEREOF, MACK-CALI REALTY, L.P. has caused this instrument to be duly executed.

Dated: December 20, 2002

TRUSTEE'S CERTIFICATE OF AUTHENTICATION:

This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture.

4

ASSIGNMENT FORM

FOR VALUE RECEIVED, the undersigned hereby
sells, assigns and transfers unto

5

QuickLinks

Exhibit 4.3