Two species of cymothoid isopods (Nerocila japonica Schioedte & Meinert, 1881 and Nerocila phaiopleura Bleeker, 1857) were collected from marine fishes in the Hibiki-Nada Sea, off the west coast of Yamaguchi Prefecture, Japan： N. japonica from the dorsal fin of Takifugu snyderi (Abe, 1988) (Tetraodontiformes： Tetraodontidae) and N. phaiopleura from the caudal surface of Scombrops gilberti (Jordan & Snyder, 1901) (Periciformes： Scombropidae). These fishes are new hosts for the Nerocila species. This represents the first record of both Nerocila species from the Hibiki-Nada Sea.