Pomacentrus vatosoa, new species, is described on the basis of four specimens collected from Nosy Faho, Madagascar. The new species is distinctive in having a pearlescent-white body with a large black spot midlaterally behind the pectoral fin, a black saddle of similar size on the dorsal edge of the caudal peduncle, and a black recurved band from the orbit to origin of dorsal fin. Aside from details in live coloration, the new species is readily diagnosed from congeners in having the following combination of characters: dorsal-fin rays XIV, 13–14; anal-fin rays II, 14; pectoral-fin rays 18–19; tubed lateral scales 19–20; gill rakers 5–6+17–18 = 22–24; infraorbitals naked; teeth on lower jaw partly biserial; no distinct notch between infraorbitals 1 and 2; and a crescent opening of the supraorbital canal above the eye. The new species appears to be most closely related to Pomacentrus atriaxillaris on the basis of meristic data, though comparative molecular sequences for P. atriaxillaris are lacking. Assignment of the new species to the genus Pomacentrus is accompanied with a brief discussion of the systematic contention within the Pomacentridae.