Macroderma gigas is a gleaner and an ambush predator. It takes large insects, frogs, reptiles, small birds, rodents and other bat species, killing with a bite to the head and neck and carrying the carcass to a feeding perch. Bones and wings accumulate below regular perches, which is how many roosts are found.
Echolocation is used, but the calls are relatively quiet and the species relies heavily on passive listening for prey-generated sound, along with large eyes that work well in low light. This is a common pattern among gleaning bats: broadcasting loudly at a target sitting on a leaf produces confusing clutter echoes, whereas the prey's own noise is unambiguous.
Two misconceptions are worth correcting. Despite the name and the false vampire bat label sometimes applied to the genus, the ghost bat does not feed on blood. And the species is not uniformly widespread: it is listed as Vulnerable, with populations sensitive to disturbance at cave and mine roosts.