Appearance and behavioral abnormalities (AA and BA, respectively) of red seabream Pagrus major infested with Ceratothoa verrucosa (usual parasitism) were described in this report. Three major and some minor AA were observed in the infested fish [major： mouth insufficiency, exophthalmos and bubble formation in the eye (BF). minor： disappearance of bubble in the eye, bulge of cornea with bubble, rupture of the swollen cornea, storage of white turbid liquid in the eye]. On the other hand, BA were classified into five categories： 1. buoyancy dysregulation (BD； three types, a, b & c), 2. protruding action of the head above the water surface (PA), 3. shivering of the body, 4. sideways swing of the head and 5. body tilt. BD and PA were general, and others were rare. Exophthalmos, BF, BD and body tilt were speculated due to the dysregulation of blood gas concentration.