A Gram-stain positive, pleomorphic, oxidase-negative, non-motile isolate from the ulcer of a farmed Atlantic salmon (Salmo salar), designated strain T11b(T), was subjected to a comprehensive taxonomic investigation. A comparative analysis of the 16S rRNA gene sequence showed highest similarities to the type strains of Pseudarthrobacter siccitolerans (98.1 %) and Arthrobacter methylotrophus and Pseudarthrobacter phenanthrenivorans (both 98.0%). The highest ANI value observed between the assembled genome of T11 b(T) and the publicly available Pseudarthrobacter and Arthrobacter type strain genomes were 81.15 and 80.99%, respectively. The major respiratory quinone was menaquinone MK-9(H-2). The polyamine pattern contained predominantly spermidine. The polar lipid profile consisted of the major lipids diphosphatidylglycerol, phosphatidylglycerol, monogalactosyl-diacylglycerol and dimannosylglyceride. Minor amouts of trimannosyldiacylglycerol and phosphatidylinositol were also detected. The peptidoglycan was of the type A3 alpha-L-Lys-L-Ser-L-Thr-L-Ala (A11.23). In the fatty acid profile, anteiso and iso branched fatty acids predominated (anteiso C-15:0, iso C-16(:0), anteiso C-12:0). Moderate to low DNA-DNA similarities, physiological traits as well as unique traits in the fatty acid pattern distinguished strain T11 b(T) from the next related species. All these data point to the fact that strain T11b(T) represents a novel species of the genus Arthrobacter for which we propose the name Arthrobacter ulcerisalmonis sp. nov. The type strain is T11b(T) (=CIP 111621(T)=CCM 8854(T)=LMG 30632(T)=DSM 107127(T)).