BACKGROUND: Electron beam irradiation and using of organic acids cause reducing or eliminating the microbial load of poultry diets. OBJECTIVES: This study was conducted to compare the effect of electron beam irradiation and organic acids on diet microbial load, immune system, serum lipids, intestinal morphology, organs relative weight and growth characters of broilers. METHODS: 300 day-old male broilers (Cobb 500) were randomly divided into 5 experimental groups, so that each group included 4 replicates with 15 birds per pen. Treatments were basal diet as control, irradiate diet by 3, 5 and 7 kGy doses and diet containing Formycin 0.2%. RESULTS: The highest and lowest of daily weight gain average were observed in finisher and total period by 7 kGy and control groups, respectively (p<0.05). Moreover, a significant reduction were observed in microbial load of diets among treatments (p<0.05). Highest (5.66) and lowest (4.17) antibody titer against SRBC were observed in Formycin and control groups, respectively (p<0.05) after 2nd injection. Highest and lowest percentage of breast weight and abdominal fat were observed in 7 kGy and control groups, respectively (p<0.05). Greatest villus height (1089 µm) and villus height to crypt depth ratio (5.84) in jejunum were obtained in 7 kGy group (p<0.05). CONCLUSIONS: Experimental dietary irradiation improves broiler perform-ance, that its trend is more evident with increasing exposure dose.