Breeding season: April–June, sometimes two broods in southern Sweden. - Nest: in cavities — natural tree holes, nest boxes (hole 32–35 mm), letterboxes, cracks in walls. - Eggs: 8–13 (record 18), pale pink with red spots. Incubated for 13–15 days by the female. - Young: both parents feed roughly 100 insects a day per chick. They fledge after 18–21 days.
The Great Tit is a dedicated cavity nester and readily takes to a nest box. The pair start inspecting nest sites as early as February–March, and the female builds a moss nest lined with animal hair and feathers on her own. Breeding is timed so that the chicks hatch just as the caterpillar peak in the deciduous trees arrives in May, giving maximum food availability during the most demanding period.