Cyrtandra lessoniana is a shrub growing 2–3(–4) meters tall, with many-branched stems that are rounded to angular and may be either pubescent with multicellular hairs or glabrate with age. The leaves are simple and opposite, borne on the upper 3–7 nodes. Within each pair, leaves are typically unequal in size but are symmetrical or nearly so. Leaf blades are lanceolate to oblanceolate, occasionally elliptic (rarely broadly so), and range from 5–21(–24) cm in length and 1.2–5.5(–7) cm in width. Leaf apices are acute to acuminate (rarely obtuse), and bases are cuneate to attenuate. The upper surface is sparsely covered with appressed hirtellous hairs, while the lower surface is densely velvety pilose, especially along the veins. Blades are firm-chartaceous to subcoriaceous in texture and distinctly rugose. Margins are entire to minutely serrulate and usually slightly revolute. Venation is strongly impressed above and usually conspicuously raised below. Petioles are (0.6–)1.5–5 cm long, and the base may clasp the stem or be perfoliate. Stipules are absent. The flowers are bisexual (perfect) and typically borne singly (rarely up to 4) in cymes in the leaf axils. These inflorescences are dense to moderately appressed pilose, with hairs occasionally spreading. Peduncles are stout and (6–)10–22 mm long, while pedicels measure 5–22 mm and may elongate to 15–33 mm in fruit. Bracts are lanceolate to elliptic, distinct or occasionally connate, and measure (5–)8–12(–18) mm long. The calyx is 2–5(6)-lobed, nearly actinomorphic (radially symmetric), white (or occasionally green) when fresh, 8–22 mm long, and cleft to the base. Calyx lobes are foliaceous, ovate to elliptic or lanceolate, somewhat unequal in size, and are densely to sparsely appressed pilose on the lower half, glabrous or glabrate above, sometimes with sparse internal pubescence. Margins are ± revolute, and apices are caudate to acuminate. Calyces may be deciduous or persistent in fruit. The corolla is usually bilabiate and white, with a cylindrical, straight, or curved tube measuring (10–)15–20 mm long and about 7–8 mm in diameter, and densely shaggy villous externally. The upper lip has two reniform lobes (2.5–5 mm long, 4–7 mm wide), and the lower lip has three rhombic–orbicular lobes (3–7 mm long, 4–8 mm wide), all imbricate in bud. Of the five stamens, only the two upper ones are fertile, while the rest are staminodial with abortive anthers. Fertile anthers are coherent in the throat of the corolla tube, dithecal, and dehisce by longitudinal slits or sometimes apical pores. The ovary is superior, oblong–ovoid, 2-carpellate but 1-celled due to parietal placentation, with two ± intruded placentas. Rarely, the placentae may meet centrally and divide the ovary into two locules. Ovules are numerous and anatropous, and the ovary apex is either rounded or ends in a short stylar beak. The style is 1–2 mm long and glabrous, and the stigma is capitate and 2-lobed, with elliptic lobes. The fruits are fleshy or firm, white berries, ovoid, measuring 1–2.3 cm long, glabrous, and often tipped by a persistent stylar beak. Seeds are numerous, ellipsoid, and minute (~0.5 mm long), with a reticulate surface. It inhabits wet forests but is also occasionally found in diverse mesic forests between 365-1,230 meters.