A taxonomic study on the genus Tropocyclops has been accomplished as a part of the series of studies on the freshwater cyclopoid copepods in South Korea. As a result, the Tropocyclops prasinus, hitherto known from Korea in many reports and papers, turns out to be a species complex of three sibling species: T. prasinus (Fischer, 1860), T. ishidai n. sp., and T. setulifer n. sp. This paper deals with description of two of these new species with taxonomic accounts on their inter- or intraspecific morphological discrepancies.