Adults are 33–36 cm (13–14 in) long. They have long pink legs, a long thin black bill and are blackish
above and white below, with a white head and neck with a varying amount of black. Males have a black back, often with greenish gloss. Females' backs have a brown hue, contrasting with the black remiges. In the populations that have the top of the head normally white at least in winter, females tend to have less black on head and neck all year round, while males often have much black, particularly in summer. This difference is not clear-cut, however, and males usually get all-white heads in winter.
Immature birds are grey instead of black and have a markedly sandy hue on the wings, with light feather fringes appearing as a whitish line in flight.
The breeding habitat of all these stilts is marshes, shallow lakes and ponds. Some populations are migratory and move to the ocean coasts in winter; those in warmer regions are generally resident or short-range vagrants. In Europe, the black-winged stilt is a regular spring overshoot vagrant north of its normal range, occasionally remaining to breed in northern European countries. Pairs have successfully bred in Britain in 1987,and after a 27-year hiatus, two instances of successful breeding in Southern England in 2014.
These birds pick up their food from sand or water. They mainly eat insects and crustaceans.
The nest site is a bare spot on the ground near water. These birds often nest in small groups, sometimes with avocets.