This study was conducted to investigate the influence of 3 levels of cheese whey as a natural source of peroxidase to overcome the negative effects of poly- phenolic compounds naturally found in feed ingredients of rabbit feed. Thirty New Zealand growing rabbits were used. The rabbits were divided according to body weight into 5 similar experimental groups. They were assigned at random to receive the 5 experimental diets. The control ration was a commercial diet. Un-decorticated cotton seed cake partially replaced soybean meal protein in the second diet. The other 3 experimental diets were the same as diet 2 but supplemented with 1, 2, and 3%. of cheese whey, respectively. The experiment lasted for 72 days to study the effects on nutrients digestibility and feeding values, growth performance, and economical efficiency. Results showed that rabbits fed diet containing 3% whey recorded significant increase in digestibility coefficients of DM, OM, CP, CF, EE and NFE compared to the other ratios while diets which contained 2 or 3% whey had higher digestibility of NDF, ADF, hemi- cellulose, cellulose and lignin. The nutritive value as TDN, DE and ME significantly (P<0.01) increased with 2 or 3% whey. Final body weights were 2545, 2248.33, 2466.67, 2470.50 and 2456.67 g. for animals fed the control, 0, 1, 2 and 3% whey, respectively. Corresponding averages of daily gains were 26.02, 21.78, 24.84, 24.85 and 24.63 g. These results revealed significant (P<0.05) improvement in growth performance in response to whey supplementation. In addition, economical efficiency and relative economic efficiency were the best for the group fed 1% whey (163.41 and 119.27%) followed by the other groups. It was concluded that cheese whey could be used as a natural source of peroxidase to ameliorate the negative effects of phenolic compounds naturally found in feed ingredients and the gossypol of cotton seeds.