This preliminary study analyzes the feeding habit of the fish Blennius cristatus inhabiting a rocky pool, in Itanhaém, south littoral of São Paulo State - Brazil. The main food items found were: Alga, Decapoda Reptantia, Mollusca and Amphipoda. The results showed that B. cristatus is an omnivorous species and probably also a trophic specialist preying on Gammaridea, but on Hyale media only, although twelve other species of the group were recorded in the sampling local.