Spiochaetopterus iheyaensis, a new species of Chaetopteridae (Annelida: Polychaeta) is described from 6 specimens collected by the Deep-Sea Research Vehicle Shinkai 2000 from the deep sea at Iheya Seamount, off Okinawa, Japan. The species is characterized by the coloration of the ventral shield of the anterior region (region A), by having one or two pairs of large cutting chaetae on the fourth chaetiger (A4), and by the morphology of A4 modified cutting chaetae (with inflated semi-circular and pear-shaped in upper view, head lacking teeth), having 2 middle region (region B) chaetigers, and a slender, annulated tube. The new species is compared to Pacific Spiochaetopterus, particularly the ultrastructure of the A4 chaetae.