Canavalia napaliensis is a perennial climbing plant in the Fabaceae (pea) family with elliptical, papery leaflets 6 to 13 cm (2.4 to 5 in) long and 3.5 to 7.5 cm (1.4 to 3 in) wide. The upper surfaces of the leaves are sparsely pubescent, and the lower surfaces are densely pubescent. Flowers number 7.6 to 40.6 cm (3 to 16 in), pseudoracemes (multiple flowers in each bracket axil) are 1.9 cm (0.8 in) long, with dark purple corollas that are white spotted at the base. The flowers are 36 to 39 mm (1.4 to 1.5 in) long with wing petals 37 to 45 mm (1.5 to 2 in) long. The fruit pods are compressed, 14 to 20 cm (5.5 to 8 in) long by 3 to 3.8 cm (1 to 1.5 in) wide and densely silky pubescent. The seeds are reddish brown, oblong-elliptic, strongly compressed, 20 to 24 mm (0.8 to 1 in) long, and 14 to 16 mm (0.55 to 0.63 in) wide.