A total of 360 monosex Oreochromis niloticus with an average body weight of 7.1±1 g were used. The fish were randomly divided into 8 equal triplicate groups (15 fish/replicate). A basal control diet was formulated to fulfil the nutrient requirements of the fish that contained 25% crude protein (CP) and 448.3 kcal/100 g. The other 7 diets (treatment diets) were supplemented with pomegranate peel (PP) at rates of 1, 2, 3, 5, 10, 15 and 20%. The fish were fed the diets 3 times daily at a rate of 5 to 7% of the body weight per day, 6 days a week for 90 days. Haematological analysis revealed that red blood cell (RBC) counts and haemoglobin levels (Hb) were significantly lower and that white blood cell (WBC) counts were significantly (P<0.01) higher in blood from fish fed the different PP-supplemented diets than in blood from fish fed the control diet. Glucose and total protein levels were increased after 90 days. Cholesterol levels were reduced by PP, while triglyceride levels were significantly increased. In addition, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly reduced in the blood of monosex Nile tilapia fed diets with different concentrations of PP. Immunological parameters (IgM levels and lysozyme activity) were significantly improved by PP supplementation. These results indicate that addition of PP to monosex O. niloticus diets improved immune status and liver and kidney function without any adverse effects on health status.