A new species of scopelocheirid amphipod, Scopelocheirus onagawae, was found during an ecological study of the marine scavenging amphipods in Onagawa Bay, Northeastern Japan. This species is closely similar to S. hopei and S. polymedus in the elongate gnathopod 1 and the broad merus of pereopod 5, but clearly distinguished from them by lateral cephalic lobe, maxilla 2, pereopod 6, epimeron 2 and uropods 1-3. This paper also describes some taxonomic commentary on the generic identity of the genus Scopelocheirus and a related genus Aroui.