The current study was carry out to assess the effects of effective microorganism(EM) as feed additive on performance, digestive enzymes, thyroid hormones, lipid profile, hepatosomatic index, immune response, enteric pathogens, and antioxidant parameters of broiler chicks. A total number of 180 broilers (Arbor Acres) one day-old were randomly into 4 groups, with three replicates of 15 chicks each. The experimental groups consist of control fed basal diet while the other three groups fed control diet supplied with 5.0, 7.5 and 10 ml EM/kg diet and labled as EM5, EM7.5, EM10, respectively. The results show that all groups received graded levels of effective microorganisms (EM), improved all the studied growth parameters during allover period as body weights, body weight gain, feed conversion ratio, growth rate and performance index, respectively. The best values for the previous growth parameters were recorded for group fed high dietary EM level. Chicks of EM5 improved their kidney functions, in term of decreasing uric acid. Also, creatinine level did not influenced by any tested diets. With regard to the liver function, the results showed a significant improvement in ALT and AST with each level of EM compared to the control group, and the best values of liver functions were for EM10. The use of EM in the feed improved serum cholesterol, HDL, LDL immune response, thyroid functions and gut microflora compared to the control group. Generally, supplementation with EM could enhance growth performance, blood biochemical and ameliorate the structure of the gut microflora.