A Gram-stain-positive, aerobic, non-motile, non-spore-forming and short rod-shaped actinomycete strain, Y4T, was isolated from a sediment sample collected from the Western Pacific. This isolate grew in the presence of 0-10 % (w/v) NaCl and at pH 6.0-9.0 and 4-40 °C; optimum growth was observed with 1 % (w/v) NaCl and at pH 7.0 and 35-37 °C. Phylogenetic analyses based on 16S rRNA gene sequence showed that strain Y4T belonged to the genus Nocardioides and was most closely related to the type strains Nocardioides ganghwensis JC2055T (98.0 %) and Nocardioides exalbidus RC825T (98.0 %), followed by Nocardioides alpinus Cr7-14T (97.9 %), Nocardioides oleivorans DSM 16090T (97.9 %), Nocardioides furvisabuli SBS-26T (97.4 %) and Nocardioides hwasunensis HFW-21T (97.4 %). Sequence similarities between strain Y4T and the other related species of the genus Nocardioides were less than 96.3 %. Strain Y4T had MK-8(H4) and MK-7(H4) as the predominant respiratory quinones and C17 : 1ω8c, iso-C16 : 0 and C17 : 0 as major fatty acids. The polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, one unknown phospholipid, two unknown glycolipids and one unknown lipid. The DNA G+C content was 70.4 mol%. The diagnostic diamino acid in the cell-wall peptidoglycan was ll-diaminopimelic acid. Strain Y4T could be differentiated from recognized Nocardioides species based on phenotypic characteristics, chemotaxonomic differences, phylogenetic analysis and DNA-DNA hybridization data. Thus, strain Y4T is considered to represent a novel species of the genus Nocardioides, for which the name Nocardioides flavus sp. nov. is proposed. The type strain is Y4T (=MCCC 1A09944T=LMG 28100T=JCM 19770T=CGMCC 1.12791T).