The coal tit is 10–11.5 cm in length, and has a distinctive large white nape spot on its black head. The head, throat and neck of the adult are glossy blue-black, setting off the off-white sides of the face (tinged grey to yellow depending on subspecies) and the brilliant white nape; the white tips of the wing coverts appear as two wingbars. The underparts are whitish shading through buff to rufous on the flanks. The bill is black, the legs lead-coloured, and irides dark brown. The young birds are duller than the adults, lacking gloss on the black head, and with the white of nape and cheeks tinged with yellow. The British breed tit has an olive hue to its brownish-grey back plumage.

Coal tits will form small flocks in winter and with other tit species. They resemble other tits in acrobatic skill and restless activity. Its food is similar to that of the others and will pick out the seeds from fir and larch cones. It will also visit gardens to feed on a variety of foods put out, particularly sunflower seeds.

A favourite nesting site is a hole in a rotting tree-stump, often low down, and the nest is deep within the hole; holes in the ground, burrows of mice or rabbits, chinks between the stones in walls, old nests of magpies or other large birds. The materials, moss, hair and grass, are closely felted together, and rabbit fur or feathers added for lining.