A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped bacterial strain, designated strain DSW4-44T, was isolated from deep-sea water from the East Sea of Korea. The optimum temperature and pH for growth were 25 °C and pH 7.5. DSW4-44T grew with 1.0-6.0 % NaCl, having optimum growth at 3-4 %. Phylogenetic analyses based on 16S rRNA gene sequences indicated that DSW4-44T represented a member of the class Alphaproteobacteria and was most closely related to Pelagicola litoralis CL-ES2T and Pelagicola litorisediminis D1-W8T, with similarities of 96.5 and 95.6 %, respectively. The major fatty acid was summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c). The polar lipids of DSW4-44T were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminolipid, two unidentified lipids and three unidentified phospholipids. The isoprenoid quinone was Q-10. The DNA G+C content of DSW4-44T was 54.3 mol%. On the basis of evidence from a polyphasic study, strain DSW4-44T represent a novel species of the genus Pelagicola, for which the name Pelagicola marinus sp. nov. is proposed. The type strain is DSW4-44T (=KCTC 62762T=KCCM 43261T=JCM 33637T).