Hazlet is a township in Monmouth County, New Jersey, United States. As of the 2010 United States Census, the township's population was 20,334, reflecting a decline of 1,044 from the 21,378 counted in the 2000 Census, which had in turn declined by 598 from the 21,976 counted in the 1990 Census.Hazlet is part of the Bayshore Regional Strategic Plan, an effort by nine municipalities in northern Monmouth County to reinvigorate the area's economy by emphasizing the traditional downtowns, dense residential neighborhoods, maritime history, and the natural beauty of the Raritan Bayshore coastline.