Exhibit 4.1

REDEEMABLE 6.375% SERIES PREFERRED H $.01 PAR VALUE THIS CERTIFICATE IS CANTON, MA, JERSEY NEW YORK, NY AND KILROY NJ, REALTY PA INCORPORATED UNDER THE LAWS OF THE STATE OF SEE ON REVERSE TRANSFER FOR RESTRICTIONS IMPORTANT AND OTHER INFORMATION CUSIP 49427F 8 REDEEMABLE 6.375% SERIES PREFERRED H $.01 PAR VALUE THIS CERTIFIES IS THE RECORD FULLY PAID AND NONASSESSABLE SHARES OF 6.375% SERIES H CUMULATIVE REDEEMABLE PREFERRED STOCK, PAR VALUE $.01 PER SHARE, OFKilroy RealtyCorporation(the “Corporation”) transferable on the books of theCorporation by the holder hereof in person or by its dulyauthorizedattorney, upon surrender of thisCertificate properly endorsed. ThisCertificate and the shares represented hereby are issued and shall beheld subjectto all of the provisions of the charter of theCorporation(the “Charter”) and the Bylaws of theCorporationand any amendmentsthereto. ThisCertificate is not valid unless countersigned and registered by the Transfer Agent and Registrar.In Witness Whereof, theCorporationhas caused thisCertificate to be executed on its behalf by its duly authorized officers. Dated: COUNTERSIGNED AND REGISTERED: COMPUTERSHARE SHAREOWNER SERVICES LLC TRANSFER AGENT AND BY AUTHORIZED EXECUTIVE VICE CHIEF FINANCIAL OFFICER PRESIDENT AND SECRETARY CHIEF EXECUTIVE

CLASSES OF STOCK THE CORPORATION IS AUTHORIZED TO ISSUE CAPITAL STOCK OF MORE THAN ONE CLASS, CONSISTING OF COMMON STOCK AND ONE OR MORE CLASSES OF PREFERRED STOCK. THE BOARD OF DIRECTORS IS AUTHORIZED TO DETERMINE THE PREFERENCES, LIMITATIONS AND RELATIVE RIGHTS OF ANY CLASS OF THE PREFERRED STOCK BEFORE THE ISSUANCE OF SHARES OF SUCH CLASS OF PREFERRED STOCK. THE CORPORATION WILL FURNISH, WITHOUT CHARGE, TO ANY STOCKHOLDER MAKING A WRITTEN REQUEST THEREFOR, A COPY OF THE CORPORATION’S CHARTER AND A WRITTEN STATEMENT OF THE DESIGNATIONS, RELATIVE RIGHTS, PREFERENCES, CONVERSION OR OTHER RIGHTS, VOTING POWERS, RESTRICTIONS, LIMITATIONS AS TO DIVIDENDS AND OTHER DISTRIBUTIONS, QUALIFICATIONS AND TERMS AND CONDITIONS OF REDEMPTION OF THE STOCK OF EACH CLASS WHICH THE CORPORATION HAS THE AUTHORITY TO ISSUE AND, IF THE CORPORATION IS AUTHORIZED TO ISSUE ANY PREFERRED OR SPECIAL CLASS AND SERIES, (i) THE DIFFERENCES IN THE RELATIVE RIGHTS AND PREFERENCES BETWEEN THE SHARES OF EACH SERIES TO THE EXTENT SET, AND (ii) THE AUTHORITY OF THE BOARD OF DIRECTORS TO SET SUCH RIGHTS AND PREFERENCES OF SUBSEQUENT SERIES. REQUESTS FOR SUCH WRITTEN STATEMENT MAY BE DIRECTED TO THE SECRETARY OF THE CORPORATION AT ITS PRINCIPAL OFFICE. RESTRICTION ON OWNERSHIP AND TRANSFER THE SHARES OF 6.375% SERIES H CUMULATIVE REDEEMABLE PREFERRED STOCK (THE “SERIES H PREFERRED STOCK”) REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON BENEFICIAL AND CONSTRUCTIVE OWNERSHIP AND TRANSFER FOR THE PURPOSE OF THE CORPORATION’S MAINTENANCE OF ITS STATUS AS A REAL ESTATE INVESTMENT TRUST UNDER THE INTERNAL REVENUE CODE OF 1986, AS AMENDED (THE “CODE”). SUBJECT TO CERTAIN FURTHER RESTRICTIONS AND EXCEPT AS EXPRESSLY PROVIDED IN THE CORPORATION’S CHARTER, (i) NO PERSON MAY BENEFICIALLY OWN SHARES OF THE CORPORATION’S SERIES H PREFERRED STOCK IN EXCESS OF 9.8% (BY VALUE OR BY NUMBER OF SHARES, WHICHEVER IS MORE RESTRICTIVE) OF THE OUTSTANDING SERIES H PREFERRED STOCK OF THE CORPORATION; (ii) NO PERSON MAY CONSTRUCTIVELY OWN SHARES OF THE CORPORATION’S SERIES H PREFERRED STOCK IN EXCESS OF 9.8% (BY VALUE OR BY NUMBER OF SHARES, WHICHEVER IS MORE RESTRICTIVE) OF THE OUTSTANDING SERIES H PREFERRED STOCK OF THE CORPORATION; (iii) NO PERSON MAY BENEFICIALLY OR CONSTRUCTIVELY OWN SERIES H PREFERRED STOCK THAT, TAKING INTO ACCOUNT ANY OTHER CAPITAL STOCK OF THE CORPORATION BENEFICIALLY OR CONSTRUCTIVELY OWNED BY SUCH PERSON, WOULD RESULT IN THE CORPORATION BEING “CLOSELY HELD” UNDER SECTION 856(h) OF THE CODE OR OTHERWISE CAUSE THE CORPORATION TO FAIL TO QUALIFY AS A REIT; AND (iv) NO PERSON MAY TRANSFER SERIES H PREFERRED STOCK IF SUCH TRANSFER WOULD RESULT IN THE CAPITAL STOCK OF THE CORPORATION BEING OWNED BY FEWER THAN 100 PERSONS. ANY PERSON WHO BENEFICIALLY OR CONSTRUCTIVELY OWNS OR ATTEMPTS TO BENEFICIALLY OR CONSTRUCTIVELY OWN SERIES H PREFERRED STOCK WHICH CAUSES OR WILL CAUSE A PERSON TO BENEFICIALLY OR CONSTRUCTIVELY OWN SERIES H PREFERRED STOCK IN EXCESS OF THE ABOVE LIMITATIONS MUST IMMEDIATELY NOTIFY THE CORPORATION. IF ANY OF THE RESTRICTIONS ON TRANSFER OR OWNERSHIP REFERRED TO IN CLAUSE (i), (ii) or (iii) ABOVE ARE VIOLATED, THE SERIES H PREFERRED STOCK REPRESENTED HEREBY IN EXCESS OF SUCH RESTRICTIONS WILL BE AUTOMATICALLY TRANSFERRED TO THE TRUSTEE OF A TRUST FOR THE BENEFIT OF ONE OR MORE CHARITABLE BENEFICIARIES. IN ADDITION, THE CORPORATION MAY REDEEM SHARES UPON THE TERMS AND CONDITIONS SPECIFIED IN THE TERMS OF THE SERIES H PREFERRED STOCK AND AS OTHERWISE SPECIFIED BY THE BOARD OF DIRECTORS IN ITS SOLE DISCRETION IF THE BOARD OF DIRECTORS DETERMINES THAT OWNERSHIP OR A TRANSFER OR OTHER EVENT MAY VIOLATE THE RESTRICTIONS DESCRIBED ABOVE. FURTHERMORE, UPON THE OCCURRENCE OF CERTAIN EVENTS, ATTEMPTED TRANSFERS IN VIOLATION OF THE RESTRICTIONS DESCRIBED ABOVE MAY BE VOID AB INITIO. ALL TERMS IN THIS LEGEND WHICH ARE DEFINED IN THE CHARTER OF THE CORPORATION SHALL HAVE THE MEANINGS ASCRIBED TO THEM IN THE CHARTER OF THE CORPORATION, AS THE SAME MAY BE AMENDED FROM TIME TO TIME, A COPY OF WHICH, INCLUDING THE RESTRICTIONS ON TRANSFER AND OWNERSHIP, WILL BE FURNISHED TO EACH HOLDER OF SERIES H PREFERRED STOCK ON REQUEST AND WITHOUT CHARGE. REQUESTS FOR SUCH A COPY MAY BE DIRECTED TO THE SECRETARY OF THE CORPORATION AT ITS PRINCIPAL OFFICE. The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations: TEN COM — as tenants in common TEN ENT — as tenants by the entireties JT TEN — as joint tenants with right of survivorship and not as tenants in common UNIF GIFT MIN ACT— Custodian (Cust) (Minor) under Uniform Gifts to Minors Act (State) UNIF TRF MIN ACT— Custodian (until age ) (Cust) under Uniform Transfers (Minor) to Minors Act (State) Additional abbreviations may also be used though not in the above list. FOR VALUE RECEIVED, hereby sell, assign and transfer unto PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE) Shares of the Series H Preferred Stock represented by the within Certificate, and do hereby irrevocably constitute and appoint Attorney to transfer the said stock on the books of the within named Corporation with full power of substitution in the premises. Dated X X THE SIGNATURE(S) TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME(S) AS WRITTEN UPON THE NOTICE: FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATSOEVER. Signature(s) Guaranteed By THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO S.E.C. RULE 17Ad-15.