Unlike most other tits, the Willow Tit excavates its own nest cavity, usually in rotten wood in a stump, a fallen log or a dead deciduous tree such as birch or alder. This makes the species dependent on dead wood in the forest. The female normally lays 6–9 eggs, which she incubates for about 13–15 days. The young are fed by both parents and fledge after a good two weeks. The Willow Tit rarely takes ordinary nest boxes, as it prefers to excavate the nest itself.