Here we present new data on relative abundance and diet of Bradypus tridactylus Linnaeus, 1758 resulting from 2,505 km of river based surveys conducted in northern Amazonia. Our sampling effort using a motorized boat provided a low number of B. tridactylus detections (n = 4, relative abundance of 0.02 individuals/ 10 km surveyed). Our observations provide the first record of Parkia velutina Benoist (Leguminosae - Mimosoideae) consumption for B. tridactylus. We contribute with recommendations of standardized complementary survey techniques that can be used to provide data on relative abundance of arboreal mammals such as sloths in tropical forests.