One species of the genus Ephedrus Haliday, 1833 (Hymenoptera: Braconidae: Aphidinae) is recognized in this study. The Ephedrus genus is known to 72 species worldwide. Of these, 16 species were reported in Korea. This genus is parasitic to groups of aphids and their relatives. Additionally, this genus is very similar to genus Toxares Haliday, 1840 in the morphology, but there is no difficulty in sympathy because there are certain morphological differences. In this study, Ephedrus blattnyi Starý, 1973 is recognized for the first time in South Korea. Information on this species has not been widely known yet. Descriptions, diagnosis distribution and illustration are provided.