In recent years, several southern coastal fish farms in Korea have experienced 2-30% mortality in striped beakperch suffering from bacterial infections during the spring. In this study, we identified a bacterium isolated from diseased striped beakperch as Pseudomonas anguilliseptica via a biochemical test and 16S rDNA sequence analysis. To evaluate the susceptibility of striped beakperch to P. anguilliseptica, 4.39×107 or 4.39×105 CFU/fish of bacteria were injected intraperitoneally at 18±1°C into fish weighing 5.5 g. Cumulative mortalities reached 100% and 45% in the 4.39×107 and 4.39×105 CFU/fish infected groups, respectively. Experimentally infected fish showed cell-associated inflammation as well as bacteria in the kidneys and spleen. This study is the first report of striped beakperch mortality caused by P. anguilliseptica, which has pathogenicity in striped beakperch.