A new species of pennellid (Pennellidae, Copepoda), Sarcotretes longirostris n. sp., is described based on specimens collected from bluefin driftfish (Psenes pellucidus Lütken) found in the stomach of short-finned pilot whale (Globicephala macrorhynchus Gray) caught in the western North Pacific off central Honshu, Japan. The new species differs from its congeners in the possession of 1) a long proboscis (longer than the cephalothorax); 2) a pair of blunt, lateral cephalothoracic processes (holdfast); and 3) a long neck that is distinctly longer than the trunk. This is the first species of copepod parasite reported from a representative of the genus Psenes.