The study was conducted to investigate the effect of dietary supplementation with turmeric powder as a natural growth promoter on performance, carcass traits, humoral immune responses and serum biochemical parameters in male broiler chickens. A total of 300 one-day-old male broiler chicks (Ross 308) were allocated to four treatments with five replicates. The dietary treatments consisted of the basal diet as control, 3.3, 6.6 and 10 g/kg turmeric powder added to the basal diet. The curcumin content of the turmeric powder was 1.16±0.03% by weight. Body weight gain and daily feed intake of chickens at different periods were not influenced by the dietary treatments. Broilers fed turmeric supplemented diets exhibited better feed efficiency over the grower and entire experimental periods in comparison with control group (P<0.05). A significant decrease (P<0.05) in abdominal fat pad and liver relative weight was observed in chickens fed the supplemented diets. Inclusion of turmeric powder also caused a marked (P<0.05) reduction in serum triglyceride concentration but no significant impact of turmeric powder was observed on antibody titer production against Newcastle and influenza viruses. The obtained results suggested that dietary inclusion of turmeric powder failed to induce any significant improvement on performance indexes except feed efficiency of broiler chickens. Nevertheless application of turmeric powder in the diet proved to have positive influence on carcass abdominal fat and serum triglyceride concentration at slaughter age.