This experiment was conducted to evaluate the effects of dietary turmeric rhizome powder (TP) on performance, blood metabolite, immune system, antioxidant status, and relative weight of organs in pre and post heat stressed broilers. Two hundred and sixty-four (264) day-old male Arian broiler chicks were randomly allotted to three dietary treatments containing 0, 0.4 or 0.8% turmeric powder. Each diet was fed to four replicates of 22 birds each. Heat stress was applied for 5 h (33°C) from 28 to 42 days. Two birds from each replicate were randomly selected and blood samples were taken to collect the serum, plasma and whole blood. These were slaughtered to determine the relative weight of organs pre (28 days PHS) and after heat stress (42 days AHS). TP did not affect feed intake, body weight, feed conversion ratio (FCR), production index, and protein and energy efficiency ratio of broilers. Blood cholesterol and low density lipoprotein (LDL) decreased and blood high density lipoprotein (HDL) increased when fed TP in PHS and AHS birds. TP did not affect serum triglyceride, protein, antibody production against sheep red blood cell (SRBC), IgG, IgM and Newcastle vaccination (ND) in PHS and AHS. TP suppressed the enzyme activity of lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) of heat stressed birds. The enzyme activity of creatine kinase (CK) in AHS and superoxide dismutase (SOD) in PHS were not affected by TP diets. TP diets increased blood activity of glutathione peroxidase (GPx) and SOD and decreased blood thiobarbituric acid reactive substances (TBARS) index. The H:L ratio, relative weight of bursa of fabircus and abdominal fat decreased in birds fed TP diets. TP diets did not alter percentage of bone Ash, and P of heat stress broilers; however, it increased bone Ca of heat stressed broilers. It can be concluded that the supplementation of TP to diets, decreased the activity of dehydrogenase enzyme, stressor index, and improved the antioxidant status without affecting performance and the immune system of heat stressed broilers. Key words: Turmeric powder, immune and antioxidant system, blood metabolite, broiler