The freshwater ichthyofauna of the Cubatão River basin was studied. This drainage belongs to the Atlantic rainforest biome in Paraná state coastal region, southern Brazil. Considering fish collection data and extensive new collections, 41 species were listed of the families Characidae, Erythrinidae, Crenuchidae, Curimatidae, Heptapteridae, Pseudopimelodidae, Callichthyidae, Trichomycteridae, Loricariidae, Gymnotidae, Cichlidae, Anablepidae, Poeciliidae, and Synbranchidae. The river studied showed the ichthyofaunistic pattern of the coastal drainages of the Atlantic rainforest biome of southeastern Brazil, characterized by a high degree of endemism. A key for species identification is provided.