One hundred and fifty broilers (1-day-old) were randomly allocated to 4 treatments. each of which had individual pens of 50 chicks and were used to investigate the effects of humic acid (HA) Saccharomyces cerevisiae (SC extract (YE), 2 x 10(8) cfu g(-1)) oil growth performance and immunity. All animals received the same basal diet based on corn and soybean meal and while HA was added to the basal diet at 0.25% and YE 0.25%, respectively. The following diet treatments were applied: (1) Basal diet + 0 additives, (2) Basal diet 0.25% HA kg of feed (3) Basal diet 0.25% YE kg of feed (4) Basal diet 0.25% HA+0.25% YE kg of feed. Each experimental group was fed ad libitum with its own diet for 42 days, During the experiment the chicks were reared at conventional ambient temperature (from 30 degrees C reducing to 21 degrees C by 3 degrees C/week) and relative humidity of 60-70%. Light was provided 24 h in a day. Performance data of each replicate was determined weekly during the experiment. All chicks were slaughtered when end of 6 weeks. Blood samples from 30 birds in each group was collected by branchial vein and were analyzed for Serum biochemical values, enzyme activities and performance characteristics were measured. Body weight, body weight gain, feed intake and carcass weight were positively influenced (p<0.05) by HA supplementation (0.25%) during the experiment. Difference among the groups in terms of gizzard, liver and biochemical parameters such as WBC, Heterophil, Lymphocyte, Monocyte, RBC, HCT were not statistically important among different treatment groups (p<0.05). But, Glucose and BUN levels were significantly decreased in groups HA and YE (p<0.05). ALP, ALT, Fe, Ca, P were not statistically significant among groups.