Thirteen specimens (205.0–284.0 mm standard length) of Giganthias immaculatus Katayama, 1954, previously recorded from the Izu-oshima island, Sagami Bay, Mie and Wakayama prefectures, Amami-oshima island, Okinawa, and the Yaeyama Islands in Japanese waters, were collected from the Osumi (Yaku-shima and Tanega-shima islands) and Tokara islands. Thereby continuous distribution of the species in the Ryukyu Islands is confirmed. The Osumi and Tokara specimens are described here in detail. Sexual dimorphism of the species is also discussed.

First records of Giganthias immaculatus (Perciformes: Giganthiidae) from the Osumi and Tokara islands, Kagoshima Prefecture, Japan, with notes on sexual dimorphism