Monophyly of Campellolebias Vaz-Ferreira & Sierra is supported by eight synapomorphies associated with the copulatory organ of males and a derived colour pattern. Three species, C. brucei Vaz-Ferreira & Sierra, C. chrysolineatus Costa, Lacerda & Brasil, and C. dorsimaculatus Costa, Lacerda & Brasil, all endemic to southern Brazil, are recognized and diagnosed by their unique colour patterns. Monophyly of Cynopoecilina is reinforced by the presence of 5-7 neuromasts on caudal fin, and sister-group relationship between Campellolebias and Cynopoecilus Regan, by the common possession of a putative ejaculatory muscular pump. Distribution patterns obtained from Cynopoecilina clades are compared with those available from other freshwater fishes, constituting a historical biogeographic hypothesis for eastern South America.