Macrobrachium is distributed globally in most biogeographical regions, and contains species with interestingmechanisms of evolution. We conducted an exhaustive survey on São Sebastião Island, the largest coastal island of the stateof São Paulo. Here we provide a list of species (M. acanthurus, M. carcinus, M. heterochirus, M. olfersi, M. potiuna) togetherwith the diagnosis, distribution, and remarks on each species, and a key for their identification. We compare our findingswith available information on the genus. The high diversity of freshwater shrimps on the island is interesting in terms ofbiogeographical and evolutionary processes.