A new species of synaptid holothurian, Leptosynapta brasiliensis n. sp., is described. The species shows affinities with Leptosynapta minuta (BECHER, 1906), presenting 12 simple tentacles and 12 dumb-bell shaped pieces constituting the calcareous ring; anchor ossicles exhibit a sharply bifurcate stock. All individuals were collected in Praia Vermelha, Rio de Janeiro - RJ, Brazil, in coarse sand, at a depth of some 3 m.