Tricolia retrolineata sp. n. is described from off-shore reef habitats in southern Mozambique and north-eastern South Africa. The smooth, glossy shell with bright, variegated colour pattern, as well as the convex, paucispiral, calcareous operculum and lack of interior nacre clearly place this species in the family Phasianellidae. The bulimoid shape of the shell, combined with its small size and lack of capillary lines in the colour pattern are typical of the genus Tricolia s.l.