Argostemma vietnamicum B.H. Quang, Joongku Lee & R.K. Choudhary, a new species of Rubiaceae from Thua-Thien Hue Province of central Vietnam is described and illustrated. It is morphologically similar to A. discolor and A. bariense, but differs from them by having considerably shorter petioles, round to obovate leaf laminae with a round base, obsolete secondary veins, 1–4-flowered inflorescences, much shorter peduncles and pedicels, different bracts, a glabrescent to glabrous calyx, and a shorter corolla tube. An identification key to the species of Argostemma known from Vietnam is provided.