The larger of only two species of the genus Noctilio, N. leporinus has a head and body length of 98-132mm and forearm length of 72-92mm. Weights are from 60-78 grams, with the males heavier than the females. Coloration is gray or dull brown along the middorsal line with paler underparts, but the upper parts of the male are a bright orange rufous.

N. leporinus has a pointed muzzle and full lips which appear swollen. The upper lips are smooth, divided by a vertical fold of skin beneath the nostrils forming a hood over the mouth. The lower lip is also smooth, with a semicircular pad at the center and additional semicircular folds under the chin. The cheeks are very elastic and can be greatly extended. The tubular nose extends a bit beyond the lips, and the nostril open forward and down. There is no nose leaf. The large, pointed ears are separate, and a tragus with a serrated outer margin is present. N. leporinus has a well-developed tail that is more than half as long as the thigh bone, extending to about the middle of the tail membrane, perforating its surface and freeing the tip of the tail. The wings are relatively long and narrow when compared to other species of Microchiroptera.

Preferred habitats include a variety of vegetative areas, but always near streams or moisture. N. leporinus usually roosts in rock clefts and fissures, dark caves and in hollow trees as well as in buildings. An unusually strong musky odor can indicate a roost of N. leporinus.

Feeding occurs in groups of 5-15 individuals. The bat skims the surface of a large river or freshwater pond in a zigzag fashion while chirping where pelicans have disturbed schools of fish. It is believed that echolocation is used to determine the size and velocity of the fish which is grabbed with the large claws of N. leporinus and quickly transferred to the bat's mouth. The fish may be eaten in flight or taken back to a roost where the bat eats while resting. There is a possibility that N. leporinus transfers the fish to its tail membrane, but it does not actually scoop the fish out of the water with this membrane as once believed. This species is also known to eat large insects such as flying ants, scarab beetles and stinkbugs.

N. leporinus roosts during the daylight in groups of 30 or so individuals. The reproductive cycle is monestrous, and one offspring is born during the wet season, offering the most food sources possible.

N. leporinus is found in Sinaloa (Mexico) to the Guianas, S Brazil, N Argentina, Paraguay, Bolivia, and Peru; Trinidad; Greater and Lesser Antilles; and S Bahamas.