A taxonomic study was carried out on the Perinereis nuntia species group of Korea by using morphological and molecular data (mitochondrial cytochrome c oxidase subunit I: mtCOI). Two species, P. mictodonta (Marenzeller, 1879) and P. wilsoni (Glasby and Hsieh, 2006), are recognized and redescribed. In this study, mtCOI gene showed a good resolution as molecular marker for species identification of the P. nuntia species group of Korea.