A taxonomic study was carried out on strain 10-D-4(T), which was isolated from a crude oil-degrading consortium enriched from surface seawater collected around Xiamen Island, PR China. Strain 10-D-4(T) grew optimally at pH 7.0-8.0 and at 25 °C. The 16S rRNA gene sequence of strain 10-D-4(T) showed the highest similarity to those of Idiomarina salinarum ISL-52(T) (94.6 %), Idiomarina tainanensis PIN1(T) (94.2 %) and Idiomarina seosinensis CL-SP19(T) (94.1 %), and showed lower similarity (92.3-94.0 %) to other members of the genus Idiomarina. The major isoprenoid quinone was ubiquinone 8 (Q-8). The major fatty acids were iso-C(13 : 0) (5.2 %), iso-C(15 : 0) (15.3 %), C(16 : 0) (14.3 %), summed feature 3 (C(16 : 1)ω6c and/or C(16 : 1)ω7c) (6.6 %), iso-C(17 : 0) (15.4 %) and C(18 : 1)ω7c (13.5 %). The G+C content of the chromosomal DNA was 50.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences, together with data from phenotypic and chemotaxonomic characterization, revealed that strain 10-D-4(T) represents a novel species of the genus Idiomarina, for which the name Idiomarina xiamenensis sp. nov. is proposed. The type strain is 10-D-4(T) ( = CCTCC AB 209061(T) = LMG 25227(T) = MCCC 1A01370(T)). We also propose the transfer of Pseudidiomarina aestuarii, described recently, to the genus Idiomarina as Idiomarina aestuarii comb. nov. (type strain KYW314(T) = KCTC 22740(T) = JCM 16344(T)).