[23] 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.

[26][27] European settlers were drawn to the area as early as 1682, attracted by the productive agricultural land.

The Central Railroad of New Jersey created the residential development in the area which it owned surrounding its train station.

The Art Color factory built in 1925 was Dunellen's principal industry and produced as many as 10 million magazines a month.

The W. F. Hall Printing Company of Chicago bought Art Color in 1931, and ran it until 1968, when it closed the plant there.

[31] According to the United States Census Bureau, the borough had a total area of 1.06 square miles (2.75 km2), all of which was land.

[8] The borough form of government used by Dunellen is a "weak mayor / strong council" government in which council members act as the legislative body with the mayor presiding at meetings and voting only in the event of a tie.

The mayor can veto ordinances subject to an override by a two-thirds majority vote of the council.

[44][45] As of 2024[update], the mayor of Dunellen is Republican Jason F. Cilento, whose term of office ends December 31, 2027.

Members of the borough council (with party and term-end year in parentheses) are Council President Teresa Albertson (R, 2024), Crisol-Iris Lantz (R, 2026), Joseph Paltjon (R, 2024), Trina G. Rios (R, 2025), Daniel Cole Sigmon (R, 2025) and Harold VanDermark (R, 2026).

[4][46][47][48][49] In October 2021, the borough council selected Harold VanDermark from a list of three candidates nominated by the Democratic municipal committee to fill the seat expiring in December 2023 that had been held by Tremayne Reid until he resigned earlier that month.

[52] For the 119th United States Congress, New Jersey's 12th congressional district is represented by Bonnie Watson Coleman (D, Ewing Township).

[55] For the 2024-2025 session, the 21st legislative district of the New Jersey Legislature is represented in the State Senate by Jon Bramnick (R, Westfield) and in the General Assembly by Michele Matsikoudis (R, New Providence) and Nancy Munoz (R, Summit).

[57] As of 2025[update], Middlesex County's Commissioners (with party affiliation, term-end year, and residence listed in parentheses) are: Director Ronald G. Rios (D, Carteret, 2027),[58] Deputy Director Shanti Narra (D, North Brunswick, 2027),[59] Claribel A.

[86] The Dunellen Public Schools serve students in pre-kindergarten through twelfth grade.

[101] The Dunellen station offers NJ Transit service on the Raritan Valley Line.

[102] There is a ticket office open only during morning rush hour and a small waiting area at this stop.

[104][105] Suburban Transit offers service between Dunellen and Atlantic City on its 700 route.