This study was investigated to evaluate the influence of feeding a natural feed additive, cinnamon powder (CP), at different levels on physiological responses, carcass traits and productive performance of broiler chicks. Ninety six unsexed seven-day old; Hubbard broiler chicks were allocated into four treatment groups. Each treatment consisted of three replicates eight birds each. The first diet was the control without CP. The second, third and fourth diets were supplied with 1, 3 and 5% cinnamon powder, respectively. Results showed that the addition of CP at 1.0, 3.0 and 5.0 % has significant effect (P<0.05) on feed conversion ratio at 1-3 WK of age, total protein, globulin, glucose, cholesterol, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), heterophiles (H), lymphocytes (L), basophiles (B) and H/L ratios at 6^th and 7^th week of age, Aspartate aminotransferase (AST) and albumin at 6^th week of age, but no significant effect was observed on BW, BW gain, feed intake at all periods and feed conversion ratio at four to six and one to six WK of age, albumin and Aspartate aminotransferase (AST) at 7^th week of age, Alanine aminotransferase (ALT), monocytes (M) and eosinophils (E) at 6^th and 7^th week of age. Moreover, the addition of CP did not have any significant effect on carcass traits except spleen and heart weight percentage. It could be concluded that the addition of CP up to 5% seems to have no effect on growth and carcass traits; but, it can be used to improve cellular immune responses for broiler chicks.