A Gram-negative, motile, strictly aerobic, violet-pigment-producing bacterium, designated strain FR1199T, was isolated from tidal flat sediment of Byunsan, South Korea. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain FR1199T represents a distinct line of descent within the genus Pseudoalteromonas. The phenotypic features of strain FR1199T were similar to those of Pseudoalteromonas phenolica and Pseudoalteromonas luteoviolacea, but several physiological and chemotaxonomical properties readily distinguished strain FR1199T from these species. Major fatty acids were straight-chain saturated (C(16 : 0)) and monounsaturated C(18 : 1)omega7c fatty acids. The DNA G+C content was 39 mol%. On the basis of polyphasic evidence, it is concluded that the isolate represents a novel species within the genus Pseudoalteromonas, for which the name Pseudoalteromonas byunsanensis sp. nov. is proposed. The type strain is FR1199T (=JCM 12483T=KCTC 12274T).