Abstract Fishes from the coastal basins of the Mid-Northeastern Caatinga ecoregion (MNCE) were first sampled by the Stanford expedition at the beginning of the 20th century, and published by Edwin C. Starks in 1913. This material included specimens from the Papary lake (= Papari lagoon) in the lower portion of the Trairí river basin, draining towards the eastern coast of Rio Grande do Norte State. In 1941, Henry Fowler provided a broad taxonomic study of the freshwater fishes from northeastern Brazil, including material from the Papari lagoon, besides describing four species assigned to this locality. However, these previous surveys focused only in the lower portion of the Trairí river basin and might be incomplete. Given this framework, the present study aimed at perform a wide ichthyofaunal inventory of Trairí river basin and compare with previously surveys performed in the regions. In 2013 and 2014, four expeditions along the whole basin, including the Papari lagoon itself, resulted in 28 species of fishes belonging to 17 families and seven orders. At Papari lagoon area 16 species were registered whereas 26 and 18 species were recorded by Starks and Fowler’s studies, respectively. Considering all records, 50 species were documented in the basin with 14 (28%) new records, including Serrapinnus potiguar, whose distribution was extended to the south. Two species described by Fowler, Pimelodella papariae and Pseudancistrus papariae, were not found in this study or in any fish collection, and are only known from their type-material. These two species can be naturally rare, locally extinct, or there were inaccuracies in their type-locality. However, species of these genera are only found in larger basins of the MNCE, which drains to the north, corroborating the latter assumption. Although not being a definitive list, the recent extensive fish surveys conducted in the MNCE’s coastal basins are helping to elucidate species’ geographic distribution and little knowing taxonomic issues.