Long-distance dispersal (LDD) is an essential event for species colonization and expansion in oceanic island ecosystems. Endozoochory by birds is an important factor promoting the LDD of plant seeds, but its contribution to interisland seed dispersal is still unclear. Here, we show possible seed dispersal by a seed predator pigeon, the Japanese wood pigeon Columba janthina, among oceanic islands in the Izu archipelago, Japan. This species is known to move among islands, which may be due to get food resources in isolated archipelagos with unstable habitat condition in each island. Intact seeds were found in 44.5% of pigeon feces. Seasonal population fluctuations and frequent movements between neighboring islands by pigeons can promote interisland seed dispersal. We found seeds from fruiting plants not located on the islands where the pigeon feces were collected, indicating the transportation by pigeons from another island. The seeds of only six species were dispersed by pigeons, and most of the dispersed seeds were from species with small seeds less than 1.5 mm in diameter. Fruits consumption and frequent interisland movement of Japanese wood pigeons might homogenize the distribution of plants with small seeds among neighboring islands.