A total of 630 Arbor Acres broiler chicks one-day old were used to study the effect of probiotic, prebiotic and/or yeast supplementation on the productive performance, immune response and slaughter traits. Chicks were divided randomly into 6 treatments and housed at deep litter in an open house system. Each treatment replicated 3 times (35 chicks per replicate). Treatments were as follows: T1 (control; chicks fed corn-soy basal diet) and in the other treatments diets were supplemented with 1g probiotic/kg diet as Lactobacillus acidophilus (T2), 1g yeast/kg diet as Saccharomyces cervisiae (5x10¹² CFU/g); (T3),1g prebiotic/kg diet as mannan-oligosaccharide (T4), 1g probiotic+1g prebiotic/kg diet (T5) or 1g yeast+1g prebiotic/kg die (T6). Results indicated that body weight, body weight gain, feed consumption and feed conversion ratio were improved and mortality rate was decreased in response to dietary biological feed additives. Body weight at 42 days of age was significantly heavier by about 29.5, 21.2, 12.4, 11.3 and 9.9% than control in the T6, T5, T4, T3 and T2, respectively. Moreover, all biological additives caused a significant increment in the count of erythrocytes, leukocytes, lymphocytes, heterophils, H/L ratio and the antibody titer against SRBC's. Dressing, internal organs and immune organs relative weights at 42 days of age were significantly improved by using biological feed additives. For all traits, the best values were obtained in T6 followed by T5. Also, T6 gave the best relative economical efficiency (14.70% more than control group). It could be recommended from this study that supplementation the biological additives to broiler diet from 0 to 42 days of age, as above mentioned, has a positive effect on the productivity, immune response, slaughter traits and the economical efficiency.