The effect of kaolin enriched diet on growth, hematology, and immune response in the grass carp Ctenopharyngodon idellus against Aeromonas hydrophila is reported. Both the infected and uninfected groups fed with kaolin enriched diet gained better weight, protein efficiency ratio (PER) and feed conversion ratio (FCR). The survival rate was 98.3% in control (C) and uninfected (UI) fed with 2 g kg−1 kaolin diet, whereas it was 95.0% in uninfected (UI) fed with 1 g kg−1 or infected (I) fed with 1 g kg−1 kaolin diets. In both groups the red blood cell (RBC) and white blood cell (WBC) counts, percentage of lymphocytes and eosinophils, level of albumin and globulin increased in uninfected (UI) fed with 1, 2, and 3 g kg−1 diets. The serum Ig level significantly increased in both groups when fed with 3 g kg−1 diet, whereas the phagocytic activity did not increase significantly. Further the respiratory burst activity in both groups significantly increased with any supplemented diet. The serum superoxide dismutase (SOD) activity increased significantly in the infected group fed with 2 g kg−1 diet and the uninfected group fed with 1 g kg−1 diet. The complement activity was significantly enhanced in both groups when fed with 1 and 2 g kg−1 diets; the lysozyme activity increased with 2 g kg−1 diet; besides the group was 5% mortality whereas 10% mortality was observed when fed with 1 or 3 g kg−1 diets. The present results suggest that C. idellus fed with kaolin enriched diet promotes growth, hematology, innate and adaptive immune response against Aeromonas hydrophila infection.