BACKGROUND: Glutamine supplementation to the pre-starter diet of broiler chicks could improve their performance during the first week of post-hatch. OBJECTIVES: This experiment was conducted to evaluate the influence of glutamine levels in the pre-starter diet on intestinal mucosa morphology and performance of broiler chicks. METHOD: A total of 160 Ross 308, one-day old broilers were used in a complete randomized block design with 3 treatments of 5 replicates. Diets were formulated to contain different levels of glutamine (0, 0.5 and 1%). Body weight and feed intake were measured at 6 and 13d. On d 0, 3, 6 and 13 post hatch, 2 birds per each replicate were weighted and killed, and samples of the duodenum, jejunum, and ileum were taken subsequently. RESULTS: Supplementation of diets with 1% glutamine improved growth performance and feed efficiency at 6 and 13 day post hatch (p<0.05). On d 3 and 6, glutamine supplementation increased villi height and width in the small intestinal significantly (p<0.05). On d 13, chicks fed glutamine added diet had a longer villi height and width than those fed the basal diet (p<0.05). Glutamine supplementation has also decreased crypt depth of jejunum and ileum at 3, 6 and 13, but increased crypt depth in duodenum at 3 and 6 d of age (p<0.05). Increase in glutamine levels of pre-starter diet increased villi height relative crypt depth of jejunum and ileum at 3 and 6 d of age. On d 13, chicks fed diet contain 1% glutamine had a higher villi height relative crypt depth than those fed the basal diet. CONCLUSIONS: Addition of 1% glutamine to the pre-starter diets improved broiler growth performance and resulted in better development of the intestinal mucosa in broiler chicks.