Sisyrinchium acre grows to a height of 15–30 cm. The flowering stems are usually broadly winged, consisting of a single long internode without cauline leaves. The leaves are simple and basal, measuring half as long to about as long as the flowering stems, with a width of 2–4 mm. The leaf surfaces are glabrous, with entire margins and parallel veins, and are sessile. Stipules are absent. The flowers are stellate and several in number, with spathes measuring 18–28 mm long. The outer spathe is longer than the inner one, sometimes with a terminal bract subtending the spathes. The flowers are bisexual (perfect) and actinomorphic (radially symmetric). The tepals are yellow, approximately 6–10 mm long, subequal, and spread horizontally. There are three stamens, with filaments measuring 2–3 mm long, distinct at least above, and anthers measuring 2–3 mm long. The ovary is inferior, obovoid, about 1.5 mm long, 3-carpellate, and 3-celled, with axile ovule placentation. The style is divided near the apex of the filament tube, with branches about 3 mm long, slender, and extending between the anthers. The fruit is a nodding capsule, pyriform, measuring 5–8 mm long and about 5 mm in diameter. The seeds are blackish, globose, approximately 1 mm in diameter, slightly flattened on one side with a shallow to deep, circular pit about half the diameter of the seed, and foveolate. It occurs in open, dry to boggy areas and subalpine shrubland between 1,550 – 2,950 meters.