The aim of this study was to research species composition, seasonality, and biomass of coprophagous beetles inhabiting moose dung in Kampinoski Park Narodowy, Poland. Field studies were performed from the beginning of March until the end of September 2016. Altogether, 19,234 specimens of coprophagous beetles representing 33 species were collected. Two evident peaks in numbers and biomass were observed during the study season, along with changes in dominance of species in consecutive months. Overall, the most abundant species were Acrossus rufipes (Linnaeus) (37%), Acrossus depressus (Kugelann) (21%), and Anoplotrupes stercorosus (Scriba) (13%). Seasonality of the most numerous species did not differ significantly from that noted by other authors from Central Europe. The collected species were divided into four groups according to the number and time of population peaks during the season. Most of the species are univoltine. only one species may be considered as bivoltine.