Lanner falcons hunt often where prey congregates, such as at waterholes or colonial nesting sites, or at grass fires, where up to 20 lanner falcons may gather to feed. The look for small to medium-sized birds, but also tak small mammals, insects, reptiles and even spiders and scorpions in deserts.
The lanner falcon usually, though not always, hunts during the day, chasing or seizing prey in the air or sometimes from the ground, and occasionally stealing food from other birds of prey. Food is sometimes caught to be eaten later. Lanner falcon pairs often hunt co-operatively, with one bird flushing out prey for the other to catch.