Thomas J. Duff was an architect noted for his design of a number of religious buildings for the Roman Catholic Archdiocese of New York during its major expansion at the beginning of the 20th century.
His firm was headquartered first at the Metropolitan Building, 1 Madison Avenue,[1] and later at 407 West 14th Street, Manhattan,[2] and in Mount Vernon in Westchester County. Duff was a member of the Architectural League of New York.[3]