We report Conilepia nigricosta (Leech, 1988) in Korea for the first time. The female of C. nigricosta is nearly identical to the female of Lithosia quadra, and it has caused confusion in the generic classification. Therefore, we reexamined their morphology and also performed to analyze DNA barcode region compared with species of other related genera. As the results, the significant diagnoses between the two species were reconfirmed and provided in the adult appearances, wing venations, and genital structures in both sexes. The DNA barcoding results also showed a large genetic distance ranging from 6.21% to 7.16% between the two species. In phylogenetic relationship for these two species as well as 28 related species of Lithosiina, C. nigricosta was clustered as a sister to L. quadra and they formed a strong monophyletic group. It supports a possibility that these two genera may be a single genus, but more detailed molecular analysis using additional genetic markers and samples is needed to resolve reliable phylogenetic relationships between the taxa examined in this study.