Canavalia napaliensis is a perennial climbing plant known for its twining branches. Its leaves are compound and alternate. The leaflets are broadly elliptic, broadly ovate, or occasionally elliptic, measuring 6–13 cm in length and 3.5–7.5 cm in width. They feature a rounded to bluntly acuminate or caudate apex and a broadly cuneate or rounded base. The upper surfaces are sparsely appressed pubescent, sometimes moderately along the veins, while the lower surfaces are densely appressed pubescent. The leaflets are chartaceous, with entire margins. The leaves are petiolate with small, caducous stipules and minute leaflet stipels. The inflorescence appears in axillary pseudoracemes containing 3–16 flowers measuring 1–9 cm long. These flowers are papilionaceous with caducous bracteoles. The calyx is 26–33 mm long, densely appressed pubescent, with a shallowly concave upper edge and an upper lip 15–22 mm long. The two lobes of the upper lip are connate except at the distal 3–4 mm, and the lowest lobe is linear-lanceolate to lanceolate, measuring 6–7 mm in length. The calyx is bilabiate and 5-lobed. The corolla is dark purple with a white spot toward the base, measuring 36–39 mm long, with wing petals 37–45 mm long and keel petals 40–43 mm long. The plant has ten stamens, with the upper stamen distinct at the base and loosely adhering to the other nine up to the middle, which are connate into a tube. The ovary is superior and stipitate with 5–20 ovules; the style is incurved and glabrous; the stigma is small and terminal. The fruits are compressed pods, measuring 14–20 cm in length and 3–3.8 cm in width, and are densely silky appressed pubescent, becoming less so as they age. Each valve of the pod has an inconspicuous sutural ridge and an additional longitudinal ridge 0.5–1.7 mm below the upper suture. The seeds are reddish brown, oblong-elliptic, strongly compressed, measuring 20–22 mm long and 14–15 mm in width; the hilum is 12–14 mm long. It is found in open, dry sites and diverse mesic forests at 5-760 meters.