Keetia magassoubiana Cheek, an evergreen rainforest climber, is described and illustrated from the Republic of Guinea, Sierra Leone, Liberia and Ivory Coast. Previously indicated as being close to, but different from, K. tenuiflora (Hiern) Bridson, it differs in the glossy, black, glabrous, epidermis of the distal stem internodes; the first internode rarely with very sparse, red adpressed hairs (vs epidermis pale white-brown, with dense, pale yellow, spreading hairs); abaxial leaf surfaces with domed domatia with a central aperture (vs domatia absent or obscure); secondary stem leaf bases acute (vs obtuse to truncate); bracts forming a laciniate sheath on the distal peduncle (vs two opposite triangular bracts) and the pyrene surface honeycombed with pits (vs entire). The species was earlier included within Canthium multiflorum (Schum. Thonn.) Hiern, now K. multiflora (Schum. Thonn.) Bridson, in the Flora of West Tropical Africa, second edition. An updated key is presented to the 16 species of the genus from West Africa. Keetia magassoubiana is provisionally assessed using the IUCN standard as Endangered [EN B1ab(iii)] due to only five of the recorded 14 locations having extant forest habitat, and because of ongoing threats of habitat clearance, mainly for agriculture but also for mining.