Islip is governed by a Town Supervisor, a position which is similar to that of a Mayor, and four council members. The council is elected on an at-large basis. Additionally, a Town Clerk and Receiver of Taxes are both duly elected. All of the elected officials serve staggered four year terms. Elections are held on odd years, except when special elections are held pursuant to state law. The current supervisor is Angie Carpenter, a Republican, who was formerly the Suffolk County Treasurer. Carpenter succeeded Tom Croci after he was elected to the New York State Senate in 2015.