This study was set out to investigate the effect of feeding alloxan-induced diabetic rats with experimental diets containing genistein at different levels (2.5; 5.0; 10.0 and 20.0 mg/kg diet) on serum glucose level, lipid profile, immunoglobulins (IgG, IgM and IgA), T lymphocytes CD⁺⁴ and CD⁺⁸, potential hepatic and renal antioxidant activity as well as body weight gain and daily food intake. Obtained data indicate that body weight gained was increased in alloxan-induced diabetic rat groups fed genistein; whereas, daily food intake did not affected. Blood glucose level, hemoglobin, hematocrit, serum lipid profile as well as both of liver and kidney functions were significantly improved throughout a dose-dependent fashion as affected by daily dose of ingested genistein. All of the antioxidant activity of hepatic and renal detoxifying enzymes were elevated in alloxan-induced diabetic rat groups throughout the same trend of genistein feeding observed in the other investigated parameters. Serum immunological indices and function were significantly increased and improved in genistein ingested rats through dose-dependant manner up to the initial ingested doses as 2.5 and 5.0 mg/kg diet, whereas, higher concentrations as 10.0 and 20.0 mg/kg diet appeared to significant decrease of all immunological indices. Genistein appears to be a safe alternative to reducing blood glucose and improve the immunity in addition to enhance both renal and hepatic antioxidant enzymes potentiality. It is concluded that dietary genistein displays a range of physiological functions which may be of multiple health benefits in diabetes, namely as an inhibitor of intestinal glucose-uptake and preventive agent for glucose-induced lipid peroxidation.