The common chaffinch is about 14.5 cm long, with a wingspan of 24.5–28.5 cm and a weight of 18–29 grams. The adult male of the nominate subspecies has a black forehead and a blue-grey crown, nape and upper mantle. The rump is a light olive-green; the lower mantle and scapulars form a brown saddle. The side of head, throat and breast are a dull rust-red merging to a pale creamy-pink on the belly. The central pair of tail feathers are dark grey with a black shaft streak. The rest of the tail is black apart from the two outer feathers on each side which have white wedges.

Males typically sing two or three different song types, and there are regional dialects also. This bird is not migratory in the milder temperatures, but vacates the colder regions in winter. It forms loose flocks outside the breeding season, sometimes mixed with bramblings.

Nests are built entirely by the female and are usually located in the fork of a bush or a tree several metres above the ground. The nest has a deep cup and is lined with a layer of thin roots and feathers. The outside is covered with a layer of lichen and spider silk over an inner layer of moss and grass.