This study aims to provide a list of fish species from the Igaraçu River and some lakes of the lower Parnaíba River, Delta do Parnaíba, northeastern state of Piauí, Brazil. Eleven collecting points were sampled in a coastal area, in a wind farm, during the dry season in November 2011. A total of 1,023 individuals of 24 species, 13 families and 6 orders were collected. The most representative families in number of species were Characidae, Cichlidae and Curimatidae, respectively. Astyanax aff. bimaculatus, Serrapinnus piaba and Psellogrammus kennedyi presented the greatest abundance and distribution among the sampling points. Oreochromis niloticus was the only alien species captured. No fishes were captured in five sampling sites. Voucher material is deposited in a new zoological collection, “Coleção Zoológica do Delta do Parnaíba”.