This study was performed to investigate the effects of marine bacteria (Paracoccus sp.) and synthetic astaxanthin (Asx) as Asx sources on coloration (skin and muscle) of rainbow trout (Onchorhynchus mykiss). In the 12-week trial duplicate groups of 30 fish (28.1 ± 0.3g) were fed one of the four experimental diets. Three experimental diets contained 30 mg Asx/kg diet of synthetic Asx, marine bacteria or combined synthetic Asx and marine bacteria. One diet was served as a control diet. The fish fed diet supplemented both marine bacteria and synthetic Asx provided the highest total carotenoids and Asx content in the skin and muscle.