The cooling performance of a traditional (control) and two stage evaporative pad cooling system (experiment), including pad and fan with tunnel ventilation, for poultry houses and the growth performance of broilers reared in these systems was compared in a study performed during extreme summer temperatures. The experimental unit had a two stage pad cooling system, which consisted of underground tubes and a box, followed by a pad cooling system with tunnel ventilation. The control unit had a traditional evaporative cooling system, including pad and fan with tunnel ventilation. Air temperature, relative humidity, and saturation efficiency were used to determine the cooling performance of the systems. Live body weight gain, feed conversion ratio, and mortality rate were used to monitor the growth performance of broilers raised in these systems. The air temperature and relative humidity of incoming house and exhausted air in the two stage pad cooling system were found to be significantly lower than those of the traditional system (P < 0.05). The cooling efficiency or saturation efficiency in the two stage cooling system was found to be slightly greater than that of the traditional system. Body weight gain was also significantly influenced by the cooling system (P < 0.05). The results indicated that two stage pad cooling is a more efficient method to alleviate heat stress in broilers during heat stress conditions and to improve growth performance.