Cresskill is a borough in Bergen County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 9,155, an increase of 582 from the 2010 census count of 8,573, which in turn reflected an increase of 827 from the 7,746 counted in the 2000 census. This town got its name from "Cress", referring to the watercress that grew in its streams, and "Kill", referring to the stream passing through.