Piscataway, New Jersey. Piscataway /pɪsˈkætəˌweɪ/ is a township in Middlesex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 56,044, reflecting an increase of 5,562 (+11.0%) from the 50,482 counted in the 2000 Census, which had in turn increased by 3,393 (+7.2%) from the 47,089 counted in 1990.