Strains JS54-2(T) and JS63-1 were isolated from seawater at Jeju, Korea. Cells of these strains were Gram-positive, non-motile, non-spore-forming, short rods and formed yellow-pigmented colonies on tryptic soy agar. The strains had chemotaxonomic markers that were consistent with their classification in the genus Microbacterium, i.e. MK-11, MK-12 and MK-10 as the major menaquinones, fatty acids that were predominantly iso- and anteiso-branched, galactose and glucose as the cell-wall sugars, peptidoglycan-type B2beta with glycolyl residues and DNA G+C contents of 69.3-69.6 mol%. A phylogenetic analysis based on 16S rRNA gene sequences showed that the strains were closely related to Microbacterium oleivorans DSM 16091(T) and Microbacterium halophilum IFO 16062(T) (with 97.7 and 97.4 % sequence similarity, respectively) and formed a separate lineage with M. halophilum in the genus Microbacterium. Data from DNA-DNA hybridization and phenotypic analyses supported the conclusion that strains JS54-2(T) and JS63-1 represent a novel species in the genus Microbacterium, for which the name Microbacterium aquimaris sp. nov. is proposed. The type strain is JS54-2(T) (=KCTC 19124(T) =DSM 19713(T)).