Monodontomerus Westwood is widely distributed genus in Torymidae Walker, and it consists of 41 species with one fossil species. In Palearctic region, 18 species are recorded, each 5 species are known from Japan and China, and 8 species from Russia. However, in South Korea, only two species are known as follows: Monodontomerus dentipes (Dalman) and M. minor (Ratzeburg). In this study, four species are newly reported and a key to South Korean species of the genus Monodontomerus Westwood, diagnosis, photos of characteristics are provided.