To evaluate the seed shadow generated by wild Japanese martens (Martes melampus), we combined data on their ranging behavior from the northern foot of Mt. Fuji, central Japan (seven males and three females) with data on gut passage time obtained from martens in Toyama Municipal Family Park Zoo (three males and one female). The movement distances varied, and mean distances for 0–1, 2–3, and 4–5 h intervals were 152.4, 734.7, and 1,162.4 m, respectively, with no significant sex difference. The mean gut passage time of ingested seeds was 7.4 h (range: 0.6–51.7 h), and two-thirds were defecated within 12 h. Seeds of fleshy fruits was frequently transported to 501–1,000 m, and 20% of ingested seeds were transported > 1,000 m from feeding sites. We found positive correlations between body size and home range of the animals in Japan and their seed dispersal distances. We conclude that Japanese martens are medium-range dispersers that can transport seeds from the source to open habitats conducive for germination and/or growth, partly due to scent marking behaviors.