Two specimens of a flathead fish, Grammoplites knappi Imamura and Amaoka, 1994, were collected from the coasts of Kochi and Tokushima Prefectures, southern Japan. Reported here for the first time from Japan, this species has been known only from the South China Sea off Thailand, Malaysia, and China. Intraspecific variation in some proportional measurements and in the serration on the pterotic ridge are probably related to the immature condition of the present specimens.
