Here we reported two unrecorded naturalized species from Korean flora. Andropogon virginicus L. of Graminaeae and Euphorbia postrata Aiton of Euphorbiaceae are collected from Dong-gu, Ulsan-si and Sinjindo-ri, Taean-gun, Chungcheongnam-do respectively. A. virginicus L. was easily distinguishable from Themeda triandras var. japonica Makino by keel on glume, 2-4 racemes and long hairy rachis. Thus, the new Korean name, 'Na-do-sol-sae', was given. E. postrata Aiton was cleary distinguished from related taxa by hairs on only edges of fruits. The new Korean name, 'Nu-un-ttang-bin-dae' was given considering the species epithet. Descriptions, illustrations and photographs showing habitat were given.