Carteret is a borough in northeastern Middlesex County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population reached 25,326, its highest decennial count ever and an increase of 2,482 from the 2010 census count of 22,844, which in turn reflected an increase of 2,135 from the 20,709 counted in the 2000 census.