Biodiversity systematic monitoring programmes have been expanding across the globe, especially in protected areas (PAs). Amongst sustainable-use PAs, medium- to large-sized mammals and birds comprise crucial groups to monitor, given their importance to forest functionality and subsistence for local residents. Here, we used 6 years of community-based monitoring data from a sustainable-use PA in the Brazilian Amazonia (Tapajós–Arapiuns Extractive Reserve) to examine the influence of anthropogenic stressors and time on the density and biomass of forest mammal and bird game species. We further assessed trends in population density of target groups over the period. A total of 1915 km of line-transect surveys were completed by trained local monitors along eight established transects, providing data from 12 medium-sized and five large-sized game genera. Generalized linear mixed models of all medium-sized species, all large species and four individual taxa (Tinamidae, Dasyproctidae, primates and Cervidae) showed that some species (e.g., Dasyprocta croconota) exhibited great density, whereas others (e.g., Tapirus terrestris and Tayassu pecari) were rarely detected. Anthropogenic variables did not affect the density and biomass of the overall medium-sized and large vertebrates. Dasyproctidae, Tinamidae and primates were the only taxa influenced by anthropogenic stressors, with negative influence occurring only for Tinamidae. Moreover, density of groups and taxa remained stable throughout the period in the Reserve, although the frequency of some species may indicate past population losses. Continuation of this monitoring programme is required to improve understanding of population fluctuations, but over the 6 years studied, game population density and biomass were not linked to anthropogenic stressors.