Indiana bats are dark grey or brown bats with soft fur. They look similar to little brown bats and northern long-eared bats. One way that scientists can tell the difference between these species is by the size of their feet and the length of their toe hairs.

Indiana bats are about 3.5 inches (nine centimeters) in length with a wingspan of 9.5 to 10.5 inches (24 to 27 centimeters). Like all bats, they must be incredibly lightweight to fly. Adults weigh an average of seven grams, less than the weight of two nickels.