Two hundred and fifty male 1-day-old broiler chicks (Ross 308) were used to investigate the effects of dietary supplementation of turmeric and cinnamon powders on meat quality and lipid peroxidation of broilers under heat stress condition. The five treatment groups were control (recommended temperature for Ross 308), heat stressed (32 ± 1 ˚C from 9:00 AM to 5:00 PM during finisher period) and heat stressed birds fed with 0.50% turmeric, 0.50% cinnamon and a blend of cinnamon and turmeric (0.25% turmeric + 0.25% cinnamon). The results showed that there were no significant differences between the treatments for ether extract, ash and crude protein contents of thigh meat at 42 day of age ( p > 0.05). Heat stress decreased the pH value and dry matter (DM) content of thigh meat, whereas the consumption of all experimental diets (turmeric, cinnamon and both of them) compensated the decreased pH and DM values due to heat stress to some extent but could not restore them to the level of control treatment ( p < 0.01). Furthermore, the thigh meat lightness was increased under heat stress ( p < 0.05). The thiobarbituric acid reactive substances and free radicals scavenging activity were increased in thigh meat of broilers reared under heat stress ( p < 0.05), while these parameters were reduced by the combination of both plants ( p < 0.01). It was concluded that heat stress reduces antioxidant properties and quality of thigh meat and dietary supplementation of turmeric and cinnamon powders together can remove the detrimental effects of heat stress on meat quality.