In Japan, more than 40 species of exotic mammals have been recognized so far and have impacted on native species and forest ecosystem. Amongst the predatory mammals (Order Carnivora), the small Indian mongoose Herpestes javanicus, domestic dog Canis familiaris, Siberian weasel Mustela sibirica, domestic ferret M. putorius furo, American mink M. vison, raccoon Procyon lotor, masked palm civet Paguma larvata, domestic cat Felis catus have colonized from foreign countries. The Japanese weasel M. itatsi, red fox Vulpes vulpes shrencki, raccoon dog Nyctereutes procyonoides, Japanese marten Martes melampus melampus have colonized from areas of Japan to the Ryukyu Islands, Hokkaido and other places, where those species were originally native. The small Indian mongoose is small-sized omnivorous carnivore and native to Iraq and northern India and extending to southern China and Indonesia, the Malay Peninsula, Hainan and Java. The distribution of the mongoose is widest and the population of the mongoose is also largest in the Family Herpestidae, thus the mongoose is thought to highly adaptive. The mongoose was widely introduced by people to control rats and snake in the West Indies during the early 1870s and Hawaii and other areas, including Japan. As the mongoose is one of most issue of invasive mammals in Japan, a full-scale control program has recently been started by the Japanese government as a model case for conservation of biodiversity in subtropical islands. We review and assess the impacts of the mongoose on native species and control practices on Amami-Ohshima Island, Japan.