The objective of this study was to evaluate the effects of 1% dietary glutamic acid on the body weight, intestinal morphometry, and anti- Newcastle antibody titers of broiler chickens submitted to heat stress. One-d-old male broiler chicks (n=120) were distributed according to a 2 x 2 factorial design with two environmental temperatures (thermoneutral or heat stress) and two diets (with 0 or 1% glutamic acid). Heat stress temperature was constantly maintained (24h/day) 5 ºC higher than the thermoneutral temperature. Diets supplied the nutritional requirements of broilers in the pre-starter (1 to 7d) and starter (8 to 21d) phases. Birds were vaccinated against Newcastle disease on d 7 via eye drop. On days 5, 10, 15, and 20, individual body weight was determined, serum samples were collected from five birds, and duodenum samples were collected from four birds per treatment. Serum anti-Newcastle antibody titers were determined by enzyme immunoassay and transformed into log10. Villus height, crypt depth, and villus: crypt ratio were measured in the duodenum. Data were analyzed by ANOVA. Chronic heat stress negatively affected body weight and intestinal morphometry during the pre-starter and starter phases, but had no effect on antibody titers. Dietary glutamic acid supplementation (1%) improved body weight and intestinal integrity of birds submitted to heat stress when compared with non-supplemented and heat-stressed birds. © 2015, Fundacao APINCO de Ciencia e Tecnologia Avicolas. All rights reserved.