This work sought to look into the impacts of glutamine in drinking water on performance, intestinal morphology and corticosterone level of chickens under different stocking densities. A total 300 male chicks randomly were divided to battery cages as 10 birds/(normal stocking density) and 15 birds/(high stocking density). The chicks received feed as (i) control diet and (ii) control diet + 5g glutamine/ liter in drinking water under normal and high stocking density for the whole experiment. On d 42, 3 chicks from each cage were randomly selected and slaughtered to collect blood and duodenal samples. The results showed significant improvement in growth performance and longer villi when chicken were supplemented with glutamine via drinking water. High stocking density impaired performance of chicks in the control diet, but not in chicken supplemented with glutamine under high stocking density condition. Moreover, high stocking density increased the level of corticosterone in the both groups. More interestingly, the rate of mortality significantly decreased in chickens fed with glutamine supplemented diet (2% when supplemented with glutamine and 5.33% without supplementation). In conclusion, glutamine supplementation via drinking water resulted in better growth performance of birds subjected to high stocking density.