Municipal offices for the Township of Green Brook are located at 111 Greenbrook Road. The 4.6-mile township was created in 1932, and is the home to the historic Washington Rock, where George Washington and the Marquis De Lafayette observed British troop movements in May and June 1777 during the Revolutionary War. The 52-acre Washington Rock State Park commemorating the site was commissioned in 1913.

Green Brook Township is governed by a five-member Township Committee. Current members include Mayor Jerry Searfoss (term expiring Dec. 31, 2013), Deputy Mayor Patrick Foccio (Dec. 31, 2012), Kenneth Hermann (Dec. 31, 2012), Edward Pfeifer (dec. 31, 2014), and Nancy Stoll (Dec. 31, 2014). The committee meets twice monthly on Mondays at 7:30 p.m. in the municipal building.

Kelly Cupit is the township administrator.

Municipal offices in the building include the township clerk's office, construction and planning offices, municipal court and the offices of the tax assessor and collector.

The municipal building is open from 8:30 a.m. to 4 p.m. Monday through Friday.