Cladosporium is prevalent across the world and characterized by dark or olivaceous colonies featuring coronate conidiogenous loci. Marine Cladosporium species have also been discovered, although they have not been extensively studied taxonomically compared to those isolated from terrestrial environments. In our study, we isolated Cladosporium species from three marine habitats (seaweed, seawater, and sediment) in two locations (the intertidal region in the Republic of Korea and the open sea in the Western Pacific Ocean) in order to investigate marine Cladosporium. Using a combination of multigenetic markers (the internal transcribed spacer, actin, and translation elongation factor 1), we discovered fourteen species, of which five were previously unknown. These novel species were C. lagenariiforme sp. nov., C. maltirimosum sp. nov., C. marinum sp. nov. in the C. cladosporioides species complex, C. snafimbriatum sp. nov. in the C. herbarum species complex, and C. marinisedimentum sp. nov. in the C. sphaerospermum species complex. We have outlined the morphological features of these novel species, along with their contrasting characteristics when compared with the already-known species. We have also provided molecular data to support our findings.