A Gram-stain-negative, aerobic, non-motile, rod- and coccus-shaped bacterium, designated strain B6-12(T), was isolated from sediment collected from the River Geumho in South Korea. In comparative 16S rRNA gene sequence analysis, the novel strain appeared to be affiliated with the class Alphaproteobacteria and to be most closely related to Kaistia adipata KCTC 12095(T), Kaistia dalseonensis DSM 18800(T), Kaistia geumhonensis DSM 18799(T), Kaistia granuli KCTC 12575(T), Kaistia soli KACC 12605(T) and Kaistia terrae KACC 12910(T), with sequence similarities of 96.2-99.1%. The predominant ubiquinone in the isolate was Q-10, major fatty acids were C(18:0), C(18:1)ω7c and C(19:0)ω8c cyclo, and genomic DNA G+C content was 63.0 mol%. Based on the phylogenetic and chemotaxonomic evidence and the results of DNA-DNA hybridizations, strain B6-12(T) represents a novel species in the genus Kaistia, for which the name Kaistia defluvii sp. nov. is proposed. The type strain is B6-12(T) ( = KCTC 23766(T) = JCM 18034(T)).