A new species is described in Tetrapetalum, a small genus of which two species have been known. Although Van Heusden (1992) stated that Tetrapetalum differs from Cyathostemma only in its dimerous flowers, Tetrapetalum seems to be more closely related with Uvaria than with Cyathostemma, because of spreading petals and unlobed stigmas. A key to the three species of Tetrapetalum is provided here.