An experiment was conducted to investigatetheeffect of xylanase supplemented diet by its role to remove anti- nutritive effect of non-starch polysaccharide (NSP) is well established and optimizing the ME utilization. A total of 315, one-day-old unsexed Cobb broiler chicks, were randomly assigned into seven experimental groups of 3 replicates each with 15 birds in each replicate. The chicks were offered corn–soybean meal basal mash diets that was prepared to contain 3000 kcal ME/kg and 23% crud protein during starter period till 21 days of age, followed by 3100 kcal ME/kg and 21% crud protein during grower period till 35 days of age, and 3200 kcal ME/kg and 19% crud protein during grower period till 42 days of age. One of the seven experimental groups was fed this diet as such to serve as control while, the remaining six groups were fed the lowered ME levels by 150 or 300 kcal compared basal diet and supplemented with 0,100 and 200 mg xylanase/kg diet during starter, grower, and finisher periods, respectively. The obtained results revealed that the highest (P<0.05) body weight and weight gain recorded of birds fed dietary T3 compared to control group. Birds fed dietary T3 and control group consumed approximately similar amounts of feed and recorded a significantly better feed conversion ratio (FCR) than the control. Relative carcass weight yielded of broilers fed dietary treatment and control basal diet were statically (P< 0.05) similar, expect those fed dietary T4 recorded a significant lower value of carcass yield compared with either control or other treatment groups. Total edible parts were significantly heavier of birds fed xylanase-supplemented diets (T3, and T6) compared with that of the control and other groups. Birds fed dietary T3 recorded the highest (P< 0.05) value of relative thymus and spleen weight compared others. While, insignificant differences were observed of bursa among other treatments. The hematological parameters (Hb, PCV, RBCs and WBCs) were significantly (p≤ 0.01) improved of birds fed dietary T3 compared with counterparty of control. Total protein, albumin and globulin were significantly increased while, the concentration of triglycerides and cholesterol were significantly decreased of birds fed dietary T3 and T2 compared with the control group.