Species inventories are relatively efficient and inexpensive tools for the monitoring of biodiversity, especially in areas that have suffered high rates of deforestation, such as the municipalities located within the “Belém Endemism Center”. This region extends from northeastern Pará to northern Maranhão and has a unique flora and fauna, but is threatened by high rates of deforestation and habitat fragmentation since it is included in the so-called “Arc of Deforestation”. Benevides is the third most impacted municipality within the metropolitan region of Belém (Pará), after Belém itself and Santa Bárbara, but the biological diversity of its freshwater fish fauna is still unknown. In the present study, 81 fish species belonging to seven orders and 23 families were identified. Characidae and Cichlidae were the families with the largest numbers of species in the Taiassuí and Benfica river basins. Two of the species – Apistogramma tucurui and Hyphessobrycon inconstans – were recorded in the state for the first time. Based on the composition analysis of the fishes, it is possible to said that the Benevides fish community is relatively well preserved, because it has high diversity of groups.