In this study, we isolated Chryseobacterium sp. from koi in Turkey. The disease outbreak occurred in fish weighing 10-300g (water temperature 9-10 degrees C) in November 2011-February 2012. The cumulative mortality rate was approximately 55% over 4 months. Infected koi exhibited anorexia, weakness, emaciation, damage to dorsal and caudal fins, grey-white skin discoloration (1-1.5cm) in the head area, large open wounds in skin with disease progression, necropsy findings, paleness of the liver, enlarged spleen and kidney, acidic fluid in the body cavity. Samples for bacteriological examinations were collected from the kidney, liver, and spleen using sterile swabs; these samples were streaked onto Anacker ordal Agar and incubated at 18 degrees C for 48 h. Five bacterial isolates were obtained from diseased fish. Phenotypic characteristics of the isolates were determined by conventional methods and rapid identification kits, API 20NE, and API ZYM. Comparative 16S rRNA gene sequence analysis demonstrated that isolate Sin57 belonged to the genus Chryseobacterium, with highest sequence similarity (98.5%) to C. aahli T68(T) and C. limigenitum SUR2.