A Gram-negative, motile, rod-shaped bacterial strain, designated S3-22(T), was isolated from a sediment sample collected from a ballast water tank of a commercial ship and subjected to a polyphasic taxonomic characterization. The isolate formed small, light-yellow, semi-translucent and circular colonies on solid complex media. The strain was oxidase- and catalase-positive and metabolized a large number of carbon sources. Chemotaxonomic analysis showed ubiquinone Q-10 as predominant respiratory quinone, phosphatidylglycerol and an unidentified glycolipid as major polar lipids and iso-C(17 : 1)ω9c, iso-C(15 : 0), C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH, C(16 : 0), iso-C(17 : 0) and C(18 : 1)ω7c as major fatty acids and the hydroxy fatty acids iso-C(17 : 0) 3-OH and C(16 : 0) 3-OH. The genomic DNA G+C content was 54.9 mol%. 16S rRNA gene sequence analysis revealed that the isolate has 96.1 % similarity to the type strain of Kordiimonas gwangyangensis, the sole described species within the order Kordiimonadales, and less than 91.0 % similarity to other recognized species. On the basis of phenotypic and genotypic data, strain S3-22(T) represents a novel species of the genus Kordiimonas, for which the name Kordiimonas lacus sp. nov. is proposed, with the type strain S3-22(T) (=CGMCC 1.9109(T) =JCM 16261(T)). An emended description of the genus Kordiimonas is also presented.