Two closely related aerobic, Gram-negative rod shaped bacteria (strain W5T and W3) were isolated from Andaman Sea. Heterotrophic growth on marine agar was observed at 15-45 �XC and pH 6-10. Strain W5T showed maximum 16S rRNA sequence similarity of 99.58% with Idiomarina marina JCM 15083T. DNA fingerprinting analysis by ERIC-REP PCR, PFGE and MLSA revealed differences in banding patterns, also DNA-DNA hybridization values were well below 70% confirming W5T to be a new species. DNA G+C content was 46.7 mol%. Major fatty acids were iso-C15:0, iso-C17:0, iso-C17:1 �s9c, iso-C13:0 3OH, iso-C11:0 3OH and C16:0. Polar lipids included phosphatidylglycerol (PG) and phosphatidylethanolamine (PE) diphosphatidylglycerol (DPG) phospholipid (PL) two aminolipids (AL) and two unidentified lipids (L1-2). Q-8 is the predominant ubiquinone. On the basis of polyphasic taxonomic study, strain W5T is considered to be representative of a new species of the genus Idiomarina, for which the name Idiomarina andamanensis sp. nov. is being proposed. The type strain W5T (= LMG 29773T = JCM 31645T) was isolated from Andaman Sea.