Plainwell is located on M-89 just east of its junction with US 131. The city of Otsego is about three miles (5 km) to the west. Kalamazoo is about ten miles (16 km) to the south and Grand Rapids about north. The Kalamazoo River flows through the center of the city.
Though it sounds somewhat common, there are no other communities named Plainwell anywhere in the United States. It is known as The Island City.