Terrestrial mammals disperse more or less specialized seeds externally on their fur; yet, their effectiveness as seed dispersers is not systematically quantified at the community level. We investigated the external seed dispersal by terrestrial mammals using camera trap data for seven years, in a Japanese cedar plantation, central Japan. Camera trapping of 3,480 trap days recorded 19,841 photos with 3,156 independent detections. Among the 16 mammal species photographed, seeds of epizoochrous plants were found in 8 mammal species. We identified at least eight epizoochorous plants. There was a positive correlation between the body weight of the mammal and the frequency of photos with epizoochorous seeds, number of epizoochorous plant species, and the average number of epizoochorous seeds in a photo (Spearman's rank correlation, frequency: ρ = 0.83, P = 0.015, number of species: ρ = 0.71, P = 0.048, number of seeds: ρ = 0.85, P = 0.007). Most epizoochorous plants were dispersed by several mammal species and Capricornis crispus was the dominant seed dispersers for epizoochorous plants, followed by Ursus thibetanus and Sus scrofa, in terms of number of plant species and seeds dispersed. More quantitative information on external seed dispersal by terrestrial mammals will become available with a wider application of camera trap technique in the future.