The Present work observations were driven of potential natural predators of existent chelonians in the Negro river, municipality of Barcelos, Amazonas, Brazil. We worked in two areas of the municipality of Barcelos: Igarape of the Rio Negro Lodge and Arira. For the scientific capture of the chelonians were used meshes and net traps, in which fish and some black caiman were also caught because entered to eat, they were registered visually and for the evidence of damage caused in the turtles. In general the Crocodylia includes in their diet turtles, being Melanosuchus niger (black cayman) registered for the first time for this work area as predator of turtles: Podocnemis erythrocephala (red-headed river turtle) and especially of Peltocephalus dumerilianus (big head Amazon turtle). The existent relationship between predator and prey in this case shows few documentation, in spite of existing a wide variety of related studies.