Dunellen is a borough in Middlesex County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 7,227, reflecting an increase of 404 from the 6,823 counted in the 2000 Census, which had in turn increased by 295 from the 6,528 counted in the 1990 Census.Dunellen was formed as a borough by an act of the New Jersey Legislature on October 28, 1887, when it broke away from Piscataway Township, based on the results of a referendum held on March 23, 1886. Dunellen's incorporation was confirmed on April 15, 1914. The borough was named for the Dunellen station of the Central Railroad of New Jersey.