Diospyros sandwicensis is a tree that grows 2–10(–15) meters tall and is notable for its hard, dark red or black wood. It features simple hairs, sometimes branched or glandular, and often has galls on its stems. The leaves are simple, alternating or sometimes subopposite, aligned in one plane. The blades are predominantly lanceolate and falcate, though occasionally elliptic or elliptic-oblong, measuring 2.2–15 cm in length and 0.9–8.2 cm in width. The leaf apex ranges from acute to attenuate, occasionally obtuse. The upper surfaces are sparsely strigose but become glabrate, while the lower surfaces are usually sparsely to moderately strigose, especially along the midrib, and may become glabrate. The leaves are pale green, sometimes with a waxy bloom, and new growth is reddish. The margins are entire, and the petioles are 0.2–1.3 cm long, somewhat strigose. Stipules are absent. The flowers are typically small and unisexual, with the plants usually dioecious or sometimes monoecious. The staminate flowers may appear in clusters of 2–5, each subtended by three broad, coriaceous, caducous, pubescent bracts. The calyx is coriaceous, three-lobed, and densely pubescent, enlarging during fruit development. The corolla is urceolate and erect, approximately 5–6 mm long. Staminate flowers feature 12–18 stamens, while pistillate flowers have vestigial ovaries and 1–4 nearly distinct to connate styles. The fruit is generally a juicy to leathery or chartaceous berry, rarely a capsule, yellow to reddish-orange, dry, with a chartaceous pericarp. It measures 1.2–2.6 cm in length and is moderately puberulent, often becoming glabrate with age and usually featuring a whitish waxy bloom. It contains 1–3 seeds, which are dark brown, ovoid–ellipsoid when solitary, and crescent-shaped when more than one, each 9–13 mm long. It is found in various dry to mesic forests and extends into wet forests at elevations from 5-1,220 meters.