Malagasy sicydiine gobies are reviewed, compared with other members of the subfamily in the Mascarene region, and a new species belonging to the genus Sicyopterus Gill, 1860 is described on the basis of material collected in northeastern Madagascar. The new species differs from Sicyopterus franouxi (Pellegrin, 1935), the only other known species of sicydiine goby inhabiting the freshwaters of Madagascar, in the number of branched rays in the second dorsal fin, the color pattern of the body and fins, the number and shape of the premaxillary teeth, and the size and number of scales on the nape and abdomen. Sicyopterus franouxi, a taxon described on the basis of a single juvenile specimen, is redescribed based on adult material. The taxonomic status of Gobius lagocephalus Pallas, 1770, a nominal sicydiine species incorrectly ascribed to the Mascarene islands of the western Indian Ocean, is discussed. This species is herein concluded to be a nomen dubium of uncertain placement beyond the subfamilial level.