To update the knowledge of the ichthyofauna of the Tumbes River basin, we provide a list of species. We report 47 species of fishes, grouped into 23 families and 11 orders. Characiformes was the most diverse order with 12 species (25.5% of the total richness), followed by Carangiformes with eight species (17%). In our study, two species are newly reported from this river basin: Pseudophallus starksii (Jordan & Culver, 1895) and Evorthodus minutus Meek & Hildebrand 1928. According to salinity tolerance, the ichthyofauna is composed of 20 primary, 14 secondary, and 13 peripheral species. Despite having the highest diversity of fish on the Peruvian Pacific slope, the Tumbes river basin is one of the most polluted coastal drainages. This study compiles information on the ichthyofauna of the entire basin, increases the known diversity of freshwater fish from trans-Andean drainages in Peru, and can be used in the management and conservation of the Tumbes River.
