The genus Agetus (Cyclopoida, Corycaeidae) has so far been identified by insufficient taxonomic information due to lack of morphological details such as mouthparts, spine lengths of each leg, ornamentation on surface of second urosomal somite. These features are considered as important morphological characteristics in classifying small cyclopoid copepods through taxonomic studies. In this study, some distinct and minute morphological characteristics are used to separate each species within Agetus, with the first redescription of A. typicus, A. flaccus, and A. limbatus from Korean waters. All three species are carefully well redescribed and comparisons with past records from other localities are provided. The zoogeographical distribution has also been summarized.