Myrsine sandwicensis is a many-branched shrub or small tree, typically ranging from 1.5–4(–7) m in height. Its branches are brown to reddish-brown and glabrous. The leaves are simple and alternate, oblanceolate or elliptic-oblanceolate to obovate blades measuring 1–3(–5.8) cm long and 0.3–1(–1.5) cm in width. The leaf apex is rounded to occasionally subobtuse, sometimes inconspicuously emarginate, and the base ranges from cuneate to attenuate. The leaves are usually dark green, with young ones having a yellow hue with a red or purple tinge, and well-distributed along the upper branches. The surfaces are coriaceous, with the upper surfaces wrinkled when dry, entire and slightly revolute margins, a prominent midrib, and venation that is otherwise obscure. The flowers are found in pedicels 3–8 mm long, glabrous, or brown puberulent and are perfect, appearing in (1)2–5 bracteolate fascicles among and below the leaves. The calyx is 4–5(6)-lobed, usually deeply so, with punctate or secretory lines, and the corolla consists of 4–5(6) pale yellowish-white petals with a reddish tinge or purple. The petals are nearly distinct or connate up to ½ their length, oblong-oblanceolate, and range from 2.5–3.5 mm in length. The fruit is a purplish-black drupe, globose, approximately 6–8 mm in diameter, containing one small, dark-colored, subglobose seed excavated at the base. It is found in mesic to wet forests and bogs between 300–1,470 meters.