Delavan Township is located in Tazewell County, Illinois. As of the 2010 census, its population was 2,061 and it contained 902 housing units.
Delavan Township is named for Edward C. Delavan, a temperance advocate from Albany, New York.
According to the 2010 census, the township has a total area of , of which (or 99.93%) is land and (or 0.07%) is water.
As per a 2010 census, the township population was 2,061 with a majority of 1,689 in Delavan City and the remainder of the township constituting 372 people. The density of population per square mile of land area stood at 68.3/sq mi (26.4 sq. km).