In this study, four nudibranch species including a samlid and three dorids from Korean waters were redescribed, which were discovered while conducting a domestic nudibranch biodiversity survey from 2021 to 2023: Samla takashigei Korshunova, Martynov, Bakken, Evertsen, Fletcher, Mudianta, Saito, Lundin, Schrödl and Picton, 2017, Diaphorodoris mitsuii (Baba, 1938), Atagema intecta (Kelaart, 1858), and Martadoris amakusana (Baba, 1987). In addition, here we provided photographs of living animals and DNA barcode data based on partial sequences of the mitochondrial COI gene. We also analyzed pairwise genetic distances of the COI gene between each species and their congeners, with which we reconstructed neighbor-joining trees to show their phylogenetic relationships and evolutionary distances.