The purpose of the current study was to evaluate the effect of yeast "Saccharomyces cerevisiae" (SC) in comparison to sodium butyrate (SB) on some haematological and biochemical indices of broiler chickens. Therefore 270 one day old Hubbard broiler chicks were divided into 5 groups. The first group: chicks received basal ration without any treatment (control group, T1), the second group (T2): chicks treated with 0.2g SB/kg, the third group (T3): chicks treated with 0.3 g SB/kg; the fourth group (T4): chicks treated with 0.2 g SC/kg and the fifth group (T5): chicks treated with 0.3 g SC/kg. The obtained results showed that administration of SB or SC showed significant improved in blood picture. Inclusion of either SB or SC caused significant (P<0.01) increases in total antioxidant capacity, and the activities of anti-oxidant enzymes. Serum MDA level recorded a significant attenuate in SC groups when compared with SB and untreated groups. In conclusion, biological (SC and SB) additions can be used as one of the useful additive for enhancing the immunity and serum anti-oxidant enzyme activities of growing broiler chicks.