Current study showed the effect of adding the synergistic mixture of oyster mushrooms and beta-glucans on the productive performance of broilers under heat stress. 300 one-day-old chicks (Ross 308) were used and randomly distributed to four-treatments. Control treatment was fed standard diet. While the second, third and fourth treatments were fed starter ration with addition synergistic mixture at level (0.5, 1, and 1.5) g / kg. while 0.250, 0.5, 0.750) g/kg of oyster mushroom and beta-glucans for the same treatments, respectively were added to final diet .Results showed a significant effect (P<0.05) in body weight, rate of weight gain, decrease in the amount of feed consumed, improve in feed conversion efficiency and decrease in mortality rate, compared to control treatment. Current study conclude that addition of the synergistic mixture at level of 1.5 g / kg to the feed improved the productive and economic performance of broiler chickens.