A medium-sized bat that is closely related to the little brown bat, the gray bat and the keen's bat. Indiana bats have brownish-gray fur with cinnamon overtones. The ears and wing membranes are blackish-brown.
Indiana bats are difficult to distinguish from little brown bats and keen's bats. The main identifying feature of the Indiana bat is a distinct keel on its calcar (the cartilaginous supporting structure on the rear edge of its tail membrane).