It is an active search-hunter, suspected of capturing most of its prey by sound, due to its ability to locate mice in complete darkness. Most food is captured on ground or from low vegetation. It also rarely eats small birds, small snakes, and insects. Rain and wind may affect hunting success. A study in Italy showed that heavy snowfall caused the diet to switch from rodents to birds.
Prey is killed by biting the back of the skull, after which the prey is often swallowed whole.
Long-eared owls sometimes leave some parts of the prey uneaten, such as entrails or wings of birds. The duration of pair-bonds is unknown. Male courtship involves advertising songs and a zigzagging aerial display. The female responds by crouching with wings drooped. Copulation lasts about 3 seconds.