Holly Hills is an unincorporated community and a census-designated place (CDP) located in and governed by Arapahoe County, Colorado, United States. Holly Hills is an enclave of the City and County of Denver. The CDP is a part of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area. The population of the Holly Hills CDP was 2,521 at the United States Census 2010. Denver post office 80222 serves the area.