Abstract: The objective of this experiment was to evaluate the influence of glutamine (Gln) supplementation in the diet of broiler chickens on the growth performance, immune response as well as some blood parameters. Two hundred fifty one day old broiler chickens were allotted into five equal groups (50 chicks per each) of mixed sex. Five experimental diets were formulated to be isonitrogenous and isocaloric with different levels of Gln, first group fed on basal diets without Gln supplementation (control group), while Gln included at 0.5, 1.0, 1.5 and 2.0% and fed to chick groups (2-5) respectively for continuous 6 weeks. The results revealed that 1% Gln supplementation significantly (p < 0.05) improved body weight. Weight gain, Feed Conversion Ratio (FCR), Protein Efficiency Ratio (PER) and Efficiency of Energy Utilization (EEU) when compared with the control, while 0.5% Gln supplementation non significantly (p>0.05) improved broiler chick performance and the higher inclusion levels had negative effect on broiler growth performance. Moreover, 1% Gln supplementation significantly (p < 0.05) improved blood pictures, phagocytic activity, antibody production and increase immune organs relative weights, while the lower and higher Gln level had no effect. Chicks fed diet with Gln supplementation at different levels had heavier intestinal relative weights and longer intestinal villi (p < 0.05) as compared with the control. The results indicate that the addition of 1 % Gln to the broiler chick's diet improves growth performance and may stimulate development of the gastrointestinal tract and immune response, while higher level had negative effects.