Several species of the genusAphidiusare well known as commercial biocontrol agents of pest aphids, and more than 130 species of the genus have been recorded worldwide. To date, only 15Aphidiusspecies have been recorded in South Korea. Using the DNA barcode region (ca. 658 bp) of mitochondrial cytochrome c oxidase subunit I (COI), we amplified sequences of 15AphidiusKorean species, aligned them in combination with 23 reference species retrieved from GenBank for comparison and identification, and then reconstructed a barcode phylogeny by the neighbour-joining method. As a result, threeAphidiusspecies were found to be new to Science. Descriptions and illustrations of the three species new to Science –Aphidius longicarpussp. nov.,A. longistigmussp. nov., andA. asiaticussp. nov.– are provided, together with their phylogenetic position within the genusAphidius. In addition, a redescription ofA. areolatus, a parasitoid of maple aphids (Peryphillusspp.), is also given.