Two species of the chloroperlid stonefly, Alloperla medlata and Sweltsa illiesi, are reported for the first time in Korea. Alloperla mediata can be distinguished by the smaller epiproct and the presence of a median sclerite under epiproct in male, and by the modified subgenital plate in female. Sweltsa illiesi can be distinguished by the presence of a pair of ridges on tergum 9 in male and upward V-shaped pattern on the center of head in adults. The line drawings of diagnostic characters and taxonomic remarks of the two species are provided with keys and comparative characters for adults of Korean Chloroperlidae.