The Tatuí river hydrographic basin locates in low Sorocaba river basin in São Paulo state, Brazil. A relatively high diversity of fish species was noticed at that place, whose habitats are also presumed to be diversified. The Tatuí river is an important tributary of Sorocaba river, with great number of smaller streams and marginal lagoons. Fishes were collected using gill-nets, purse seines, sieves and traps, line and hook, every month during one year (from May 2009 to April 2010). Fish species were 51, including seven orders and 18 families. Characiformes and Siluriformes were the most represented with respectively 26 and 14 species.