The fieldfare is easily recognisable with its slate-grey head, nape and rump, dark brown back, blackish tail and boldly speckled breast. In flight, its white under wing-coverts and axillaries are conspicuous. The harsh flight call "tsak tsak" is also distinctive.
The forehead and crown of the male are bluish-grey and each feather has a central brownish-black band. The lores and under-eye regions are black and there are faint, pale streaks above the eyes. The ear coverts, nape, hind neck and rump are bluish-grey, usually with a white streak near the shaft of each rump feather. The scapulars and mantle feathers are dark chestnut-brown with dark central streaks and pale tips. There are fourteen tail feathers each with a pointed tip, the outer two slightly shorter than the others giving a rounded tail. They are brownish-black, with inconspicuous darker bars visible in some lights. The outer edge of each tail feather is fringed with grey near the base and the outer pair of feathers have a narrow white border on the inner edge. The chin, throat and upper breast are creamy-buff with bold streaks and speckles of brownish-black. The lower breast is creamy-white with a diminishing buff tinge and fewer speckles and the belly is similarly creamy-white, with the speckles restricted to the uppermost parts. The primaries are brownish-black with the leading edge fringed grey and the inner edge of the outer feathers grey near the base whereas the inner feathers are fringed with brown near the base. The secondaries are similar but fringed with chestnut-brown on the leading edge. The upper wing-coverts are brownish-black and similar to the outer primaries in their margin colouration. The axillaries and under wing-coverts are white and the under tail-coverts have dark greyish-brown bases and margins and white centres and tips. The beak is strong, with a slight curve and a notch near the tip. It is orange-yellow in winter, with the upper mandible somewhat brownish and both mandible tips brownish-black. In the summer both mandibles of the male's beak are yellow. The irises are dark brown and the legs and feet are brown. The average adult length is 25 cm (9.8 in), the winglength is 14.5 cm (5.7 in) and the tarsal length 3.5 cm (1.4 in). Wingspan ranges from 39 to 42 cm and weight ranges from 80 to 140 g.
The female is very similar to the male but the upper parts are somewhat more brownish and the feathers on the crown have narrower black central stripes. The throat and breast are paler with fewer, smaller markings. The beak is similar to the male's winter beak. The juvenile are a duller colour than the adults with pale coloured streaks on the feathers that have dark streaks in the adult. The young assume their adult plumage after their first moult in the autumn.
The call is mostly uttered in flight and is a harsh "tsak tsak tsuk". The same sound, but softer, is made more conversationally when individuals gather in trees. When angry or alarmed they emit various warning sounds reminiscent of the mistle thrush (Turdus viscivorus). The male has a rather feeble song that he sings in the breeding season. It is a mixture of a few phrases like those of the common blackbird (Turdus merula) interspersed with whistles, guttural squeaks and call notes. This is sung on the wing and also from a tree and a subdued version of this song with more warbling notes is sung by a group of birds at communal roosts.
In the summer the fieldfare frequents mixed woodland of birch, alder, pine, spruce and fir, often near marshes, moorland or other open ground. It does not avoid the vicinity of humans and can be seen in cultivated areas, orchards, parks and gardens. It also inhabits open tundra and the slopes of hills above the tree line. In the winter, groups of fieldfares are chiefly found in open country, agricultural land, orchards and open woodland. They are nomadic, wandering wherever there is an abundance of berries and insects. Later in the year they move on to pastureland and cultivated fields.
Migration southwards from the breeding range starts in October but the bulk of birds arrive in the United Kingdom in November. Some of these are still on passage and carry on into continental Europe but others remain. The passage-migrants return in April and they and the resident migrants depart from the United Kingdom mostly by early May.