Hylodes nasus is a hylodid frog species that inhabits streams in the Brazilian Atlantic Rainforest of southeastern Brazil. It is endemic to the Tijuca Massif, which includes one of the largest urban forests in the world, the Tijuca National Park, in Rio de Janeiro. We studied the diet, activity period, habitat use, and reproductive effort of H. nasus during its reproductive period. Our results showed that the species has a wide spectrum of prey items (21 categories) but feeds mainly on five prey categories (Diptera, Formicidae, Coleoptera, larvae, and other Hymenoptera). The species is diurnal and tends to present a slight decrease in activity near midday. We noted a change in microhabitat use between active (diurnal) and inactive (nocturnal) periods: active individuals mainly occupied stones, whereas inactive individuals mainly occupied low vegetation. The ovarian complement comprises a median of 88 oocytes with a mean diameter of 2.2 mm. The gathered information consists in a first approximation of the biological and ecological characteristics of the species.