Touchardia oahuensis is a species of shrub or small tree, reaching heights between 2–8 meters, characterized by its many-branched, somewhat drooping structure and brown bark. The leaves are alternate and vary in shape from delicate–lanceolate to ovate or narrowly elliptic–lanceolate, measuring (9.5–)15–36 cm in length and (3.2–)4–12 cm in width. They feature an acuminate apex and a broadly cuneate to truncate base. While the upper surfaces of the leaves are glabrous, the lower surfaces may be sparsely short–hirtellous along the veins or entirely glabrous, with some regional variations exhibiting red veins and petioles. The leaves are palmately 3-veined at the base, with 12–15 additional pairs of pinnate veins attached to 2–14.5 cm long petioles. It exhibits sexual dimorphism, with separate male and female flowers. The flowers are grouped in dichotomous, widely spreading, paniculate cymes arising from the lower leaf axils. The male (staminate) flowers are clustered in sessile glomerules with a greenish-white calyx that may exhibit violet, pink, or red hues, depending on the region. The female (pistillate) flowers are more delicate and feature a green, ovoid–ellipsoid calyx. The fruit is an ovoid, slightly compressed achene enclosed by an enlarged, fleshy calyx, which is orange or yellow when ripe. The seeds are one per achene. It is found in slopes and gulch bottoms in mesic to wet and diverse mesic forests between 150-1700 meters.