The adult white hawk (Leucopternis a. albicollis) ranges from 46–56 cm long with very broad wings and has a white head, body and underwings. The upper wings are black, and the very short tail is black with a broad white band. The bill is black and the legs are yellow.

The sexes are similar, but females are larger and heavier (840 g compared to the male’s 650 g). Immature birds have extensive black spotting on the upperparts and dark-streaked whitish underparts.

The call of the white hawk is a plaintive kerwee.