EX-31
Rule 13a-14(d)/15d-14(d) Certifications.





I,
Scott Epperson, certify that:



1. I
have reviewed this report on Form 10-K and all reports on Form 10-D required to
be filed in respect of the period covered by this report on Form 10-K of the
Benchmark 2020-B21 Mortgage Trust (the "Exchange Act periodic
reports");



2.
Based on my knowledge, the Exchange Act periodic reports, taken as a whole, do
not contain any untrue statement of a material fact or omit to state a material
fact necessary to make the statements made, in light of the circumstances under
which such statements were made, not misleading with respect to the period
covered by this report;



3.
Based on my knowledge, all of the distribution, servicing and other information
required to be provided under Form 10-D for the period covered by this report
is included in the Exchange Act periodic reports;



4.
Based on my knowledge and the servicer compliance statements required in this
report under Item 1123 of Regulation AB, and except as disclosed in the
Exchange Act periodic reports, the servicers have fulfilled their obligations
under the servicing agreements in all material respects; and



5. All
of the reports on assessment of compliance with servicing criteria for
asset-backed securities and their related attestation reports on assessment of
compliance with servicing criteria for asset-backed securities required to be
included in this report in accordance with Item 1122 of Regulation AB and
Exchange Act Rules 13a-18 and 15d-18 have been included as an exhibit to this
report, except as otherwise disclosed in this report. Any material instances of
noncompliance described in such reports have been disclosed in this report on
Form 10-K.



In
giving the certifications above, I have reasonably relied on information
provided to me by the following unaffiliated parties:



Midland
Loan Services, a Division of PNC Bank, National Association, as Master
Servicer, LNR Partners, LLC as Special Servicer, Wells Fargo Bank, National
Association, as Trustee and Certificate Administrator, Wells Fargo Bank,
National Association, as Custodian, Park Bridge Lender Services LLC, as
Operating Advisor, Computershare Trust Company, National Association, as
Servicing Function Participant for the Certificate Administrator, Computershare
Trust Company, National Association, as Servicing Function Participant for the
Custodian, Midland Loan Services, a Division of PNC Bank, National Association,
as Primary Servicer for the White Oak Crossing Mortgage Loan, CWCapital Asset
Management LLC, as Special Servicer for the White Oak Crossing Mortgage Loan,
Wilmington Trust, National Association, as Trustee for the White Oak Crossing
Mortgage Loan, Citibank, N.A., as Custodian for the White Oak Crossing Mortgage
Loan, Park Bridge Lender Services LLC, as Operating Advisor for the White Oak
Crossing Mortgage Loan, U.S. Bank National Association, as Servicing Function
Participant for the White Oak Crossing Mortgage Loan, Midland Loan Services, a
Division of PNC Bank, National Association, as Primary Servicer for the Kings
Plaza Mortgage Loan, Midland Loan Services, a Division of PNC Bank, National
Association, as Special Servicer for the Kings Plaza Mortgage Loan prior to
April 27, 2023, K-Star Asset Management LLC, as Special Servicer for the Kings
Plaza Mortgage Loan on and after April 27, 2023, Wells Fargo Bank, National
Association, as Trustee for the Kings Plaza Mortgage Loan, Wells Fargo Bank,
National Association, as Custodian for the Kings Plaza Mortgage Loan, Pentalpha
Surveillance LLC, as Operating Advisor for the Kings Plaza Mortgage Loan,
Computershare Trust Company, National Association, as Servicing Function
Participant for the Custodian for the Kings Plaza Mortgage Loan, KeyBank
National Association, as Primary Servicer for the MGM Grand & Mandalay Bay
Mortgage Loan, Situs Holdings, LLC, as Special Servicer for the MGM Grand &
Mandalay Bay Mortgage Loan, Wilmington Trust, National Association, as Trustee
for the MGM Grand & Mandalay Bay Mortgage Loan, Citibank, N.A., as
Custodian for the MGM Grand & Mandalay Bay Mortgage Loan, U.S. Bank
National Association, as Servicing Function Participant for the MGM Grand &
Mandalay Bay Mortgage Loan, Wells Fargo Bank, National Association, as Primary
Servicer for the 711 Fifth Avenue Mortgage Loan, KeyBank National Association,
as Special Servicer for the 711 Fifth Avenue Mortgage Loan, Wilmington Trust,
National Association, as Trustee for the 711 Fifth Avenue Mortgage Loan, Wells
Fargo Bank, National Association, as Custodian for the 711 Fifth Avenue
Mortgage Loan, Park Bridge Lender Services LLC, as Operating Advisor for the
711 Fifth Avenue Mortgage Loan, CoreLogic Solutions, LLC, as Servicing Function
Participant for the 711 Fifth Avenue Mortgage Loan, Computershare Trust
Company, National Association, as Servicing Function Participant for the
Custodian for the 711 Fifth Avenue Mortgage Loan, Midland Loan Services, a
Division of PNC Bank, National Association, as Primary Servicer for the Redmond
Town Center Mortgage Loan, Rialto Capital Advisors, LLC, as Special Servicer
for the Redmond Town Center Mortgage Loan, Wilmington Trust, National
Association, as Trustee for the Redmond Town Center Mortgage Loan, Citibank,
N.A., as Custodian for the Redmond Town Center Mortgage Loan, Pentalpha
Surveillance LLC, as Operating Advisor for the Redmond Town Center Mortgage
Loan, U.S. Bank National Association, as Servicing Function Participant for the
Redmond Town Center Mortgage Loan, Midland Loan Services, a Division of PNC
Bank, National Association, as Primary Servicer for the 4 West 58th Street
Mortgage Loan, Argentic Services Company LP, as Special Servicer for the 4 West
58th Street Mortgage Loan, Wells Fargo Bank, National Association, as Trustee
for the 4 West 58th Street Mortgage Loan, Wells Fargo Bank, National
Association, as Custodian for the 4 West 58th Street Mortgage Loan, Pentalpha
Surveillance LLC, as Operating Advisor for the 4 West 58th Street Mortgage Loan,
Computershare Trust Company, National Association, as Servicing Function
Participant for the Custodian for the 4 West 58th Street Mortgage Loan, Midland
Loan Services, a Division of PNC Bank, National Association, as Primary
Servicer for The Hub Mortgage Loan, Argentic Services Company LP, as Special
Servicer for The Hub Mortgage Loan, Wells Fargo Bank, National Association, as
Trustee for The Hub Mortgage Loan, Wells Fargo Bank, National Association, as
Custodian for The Hub Mortgage Loan, Pentalpha Surveillance LLC, as Operating
Advisor for The Hub Mortgage Loan, Computershare Trust Company, National
Association, as Servicing Function Participant for the Custodian for The Hub
Mortgage Loan, Wells Fargo Bank, National Association, as Primary Servicer for the
Cambridge Crossing Mortgage Loan, Situs Holdings, LLC, as Special Servicer for
the Cambridge Crossing Mortgage Loan, Wilmington Trust, National Association,
as Trustee for the Cambridge Crossing Mortgage Loan, Wells Fargo Bank, National
Association, as Custodian for the Cambridge Crossing Mortgage Loan, Park Bridge
Lender Services LLC, as Operating Advisor for the Cambridge Crossing Mortgage
Loan, CoreLogic Solutions, LLC, as Servicing Function Participant for the Cambridge
Crossing Mortgage Loan, Computershare Trust Company, National Association, as
Servicing Function Participant for the Custodian for the Cambridge Crossing
Mortgage Loan, Wells Fargo Bank, National Association, as Primary Servicer for
The Grace Building Mortgage Loan, Situs Holdings, LLC, as Special Servicer for
The Grace Building Mortgage Loan, Wilmington Trust, National Association, as
Trustee for The Grace Building Mortgage Loan, Wells Fargo Bank, National
Association, as Custodian for The Grace Building Mortgage Loan, Park Bridge Lender
Services LLC, as Operating Advisor for The Grace Building Mortgage Loan,
CoreLogic Solutions, LLC, as Servicing Function Participant for The Grace
Building Mortgage Loan, Computershare Trust Company, National Association, as
Servicing Function Participant for the Custodian for The Grace Building
Mortgage Loan, KeyBank National Association, as Primary Servicer for the
416-420 Kent Avenue Mortgage Loan, Situs Holdings, LLC, as Special Servicer for
the 416-420 Kent Avenue Mortgage Loan, Wilmington Trust, National Association,
as Trustee for the 416-420 Kent Avenue Mortgage Loan, Citibank, N.A., as
Custodian for the 416-420 Kent Avenue Mortgage Loan, Pentalpha Surveillance
LLC, as Operating Advisor for the 416-420 Kent Avenue Mortgage Loan, U.S. Bank
National Association, as Servicing Function Participant for the 416-420 Kent
Avenue Mortgage Loan, Wells Fargo Bank, National Association, as Primary
Servicer for the McClellan Business Park Mortgage Loan, Greystone Servicing
Company LLC, as Special Servicer for the McClellan Business Park Mortgage Loan,
Wilmington Trust, National Association, as Trustee for the McClellan Business
Park Mortgage Loan, Wells Fargo Bank, National Association, as Custodian for
the McClellan Business Park Mortgage Loan, Park Bridge Lender Services LLC, as
Operating Advisor for the McClellan Business Park Mortgage Loan, CoreLogic
Solutions, LLC, as Servicing Function Participant for the McClellan Business
Park Mortgage Loan, Computershare Trust Company, National Association, as
Servicing Function Participant for the Custodian for the McClellan Business
Park Mortgage Loan, Midland Loan Services, a Division of PNC Bank, National
Association, as Primary Servicer for the JW Marriott Nashville Mortgage Loan,
CWCapital Asset Management LLC, as Special Servicer for the JW Marriott
Nashville Mortgage Loan, Wilmington Trust, National Association, as Trustee for
the JW Marriott Nashville Mortgage Loan, Citibank, N.A., as Custodian for the
JW Marriott Nashville Mortgage Loan, Park Bridge Lender Services LLC, as
Operating Advisor for the JW Marriott Nashville Mortgage Loan, and U.S. Bank
National Association, as Servicing Function Participant for the JW Marriott
Nashville Mortgage Loan.







Dated: March 14, 2024





/s/
Scott Epperson

Scott
Epperson

Chief
Executive Officer

(senior
officer in charge of securitization of the depositor)