Thirty five juveniles belonging to the genus Collichthys were collected using a bag net at Gang-wha-do, in the eastern Yellow Sea, between July and September, 2012, and identified using combined genetic and morphological methods. We sequenced 316 base pairs of mitochondrial DNA cytochrome c oxidase subunit I of 35 individuals, of which 22 individuals were identified as Collichthys niveatus (12.9-47.6 mm in SL) and 13 as Collichthys lucidus (13.4-40.3 mm SL). Morphologically, the number of occipital crests, an important taxonomic character during the adult stage, could not distinguish the two species during the juvenile stage, but the shape of the first anal fin spine clearly distinguished the two species even among juveniles.