The long-eared owl is of a slenderer build than the tawny owl and has distinctive ear tufts; these tufts are simply feathers and have no connection with the actual ears. In flight, the long-eared owl keeps its ear tufts flat against its head. One of the most nocturnal of owls, it preys on rats, mice, shrews, moles, bats, squirrels, rabbits and other small mammals, as well as on birds and insects. During the day, long-eared owls roost in trees. Their mottled brown plumage helps them blend in with their surroundings. Long-eared owls roost from March to May, according to area; when food supplies are abundant they may produce two broods.  The female lays 3 to 10 eggs, usually 4 or 5, in an old nest of another bird species or even in a squirrel's nest. If no such nest is available, she will lay her eggs on the ground under a tree or bush. She incubates the eggs for 26 to 28 days, and her partner brings food to her both during this period and once the chicks are hatched. The young leave the nest 3 to 4 weeks after hatching.

Some northern populations of long-eared owls migrate south of their breeding areas in winter, to Mexico, northern Egypt and India, and northward again in spring.