Myrsine alyxifolia is a many-branched shrub or small tree reaching 2–6 m heights. The branches are brown to reddish brown and can be glabrous to sparsely reddish brown puberulent. The leaves are simple and alternate, with blades that are oblanceolate to narrowly elliptic, measuring 1.5–4.2 cm in length and 0.6–1.5 cm in width. The apex is rounded to bluntly acute, rarely acute, and may occasionally be minutely notched. The base is cuneate to sometimes attenuate. Leaf surfaces are glabrous and punctuated with black markings, appearing yellowish-green or occasionally medium green, more or less well-distributed along the upper branches. The upper surfaces are slightly glossy, while the lower surfaces are dull, pale, and slightly fleshy, becoming wrinkled when dry. The margins are entire and revolute. The midrib is prominent, though the venation is otherwise obscure. The petioles are 1–5 mm long and can be glabrous to sparsely brown puberulent. Stipules are absent. The flowers are arranged in bracteolate fascicles of (3)4–6 among and below the leaves, with pedicels measuring 4–5 mm long and sparsely brown puberulent or glabrous. The flowers are bisexual (perfect). The calyx consists of 4–5(6) lobes, which are usually deeply divided, imbricate or valvate in bud, and measure 0.6–1 mm long with ciliate margins. The corolla is also 4–5(6)-lobed, with the lobes nearly distinct or connate up to ½ their length, imbricate in bud, and oblong–oblanceolate, measuring approximately 2–2.5 mm long, with black raised secretory lines and ciliate margins. Stamens are inserted on the corolla throat, and the anthers are 1.8–2.2 mm long, with a tuft of hairs at the apex. The fruit is a drupe that matures to a purplish black color, approximately 5–7 mm in diameter. Each fruit contains a single small, dark-colored, subglobose seed excavated at the base. It is found in diverse mesic forests and occasionally in wet forests between 580-1,220 meters.