Delaware Township is a township in Hunterdon County, New Jersey, United States. Part of the township is on the Hunterdon Plateau, while the southern portions are in the Amwell Valley. As of the 2010 United States Census, the township's population was 4,563, reflecting an increase of 85 (+1.9%) from the 4,478 counted in the 2000 Census, which had in turn declined by 34 (-0.8%) from the 4,512 counted in the 1990 Census.