The effect of carotenoid-supplementation diet on immune response and disease resistance in common carp, Cyprinus carpio against Aeromonas hydrophila at weeks 1, 2, and 4 is reported. The cumulative mortality was 10% when fish were fed with 50 or 100 mg kg(-1) supplementation diets while the un-supplementation diet treated group suffered 90% mortality against the pathogen. The phagocytic activity and complement activity significantly increased with 50 and 100 mg kg(-1) diet groups from weeks 2 and 4 but not in other groups. The reactive oxygen species (ROS) production was significantly enhanced with 50 and 100 mg kg(-1) diets from weeks 1 to 4 while the production of reactive nitrogen species (RNS) enhanced on weeks 2 and 4. The lysozyme activity significantly increased when fed with 50 and 100 mg kg(-1) diets on weeks 2 and all supplementation diets on week 4. These results suggest that diet enriched with carotenoid pigment positively enhance the immune status and protects C. carpio from A. hydrophila infection.