A Gram-negative-staining, non-motile, non-spore-forming and strictly aerobic bacterial strain, SC35(T), was isolated from tidal flat sediment collected from the South Sea, Korea, and subjected to a taxonomic study using a polyphasic approach. The organism grew optimally at 20-30 degrees C and with 1-2 % (w/v) NaCl. Strain SC35(T) contained ubiquinone-8 as the predominant respiratory lipoquinone and C(18 : 1)omega9c as the major fatty acid. The DNA G+C content was 48.5 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain SC35(T) formed a lineage within the genus Psychrobacter (94.3-96.5 % sequence similarity), forming a distinct branch in a clade also containing Psychrobacter pacificensis NIBH P2K6(T) and Psychrobacter celer SW-238(T). On the basis of phenotypic and phylogenetic data, strain SC35(T) (=KCTC 22503(T)=JCM 16343(T)) was placed in the genus Psychrobacter as the type strain of a novel species, for which the name Psychrobacter aestuarii sp. nov. is proposed.