A halophilic gamma-proteobacterium, designated CL-SP19T, was isolated from hypersaline water from a solar saltern located in Seosin, Korea. Analysis of the 16S rRNA gene sequence revealed an affiliation with the genus Idiomarina. The sequence similarities between CL-SP19T and type strains of the genus Idiomarina ranged from 95.9 to 96.9 %. Cells were straight or slightly curved rods and were motile by means of a single polar flagellum. The major fatty acids were C(15 : 0) iso (17.1 %) and C(17 : 0) iso (15.2 %). Three fatty acids, C(19 : 0)omega8c cyclo (3.5 %), C(14 : 1)omega5c (1.4 %) and C(18 : 3)omega6c (1.2 %), were found in minor quantities, but uniquely in CL-SP19T among Idiomarina species. The DNA G+C content was 45.0 mol%. On the basis of its physiology, fatty acid composition and 16S rRNA gene sequence, strain CL-SP19T could be assigned to the genus Idiomarina but distinguished from the recognized species of the genus. Strain CL-SP19T, therefore, represents a novel species, for which the name Idiomarina seosinensis sp. nov. is proposed, with CL-SP19T (=KCTC 12296T=JCM 12526T) as the type strain.