The aim of this study was to evaluate the effect of using graded levels of capsaicin on growth performance, nutrients digestibility coefficients, serum metabolites, oxidative responses and intestinal digestive enzymes activity of Pekin ducks. One hundred and twenty 14d old Pekin ducks were randomly divided into four groups of 30 ducks. The first group was fed on the basal diet (control), while groups 2, 3 and 4 were given the basal diet supplemented with 50, 100 and 150 ppm capsaicin, respectively. The results showed significant improvement in body weight and feed conversion of ducks, particularly with the high level (150ppm) followed by those of the mid one (100pm). Moreover, supplemental capsaicin with different levels enhanced digestibility coefficient values especially with ether extract (EE) and nitrogen free extract (NFE) in Pekin ducks. The serum level of total proteins, globulin, high density lipoprotein (HDL), triiodothyronine (T3), thyroxin (T4) and antioxidant enzymes was significantly increased for ducks fed on diets contained either 100 or 150ppm capsaicin. But, the concentrations of total lipid, cholesterol, triglycerides, low density lipoprotein (LDL), glucose and malondialdehyde (MDA), which is the primary stable by-product of lipid peroxidation, were reduced. On the other hand, the albumin level didn't significantly affected by dietary capsaicin supplementation. A significant increase in the activities of amylase, lipase and trypsin enzymes was found throughout the small intestine portions with supplemental capsaicin. It is concluded that, capsaicin supplementation with 100ppm up to 150ppm was sufficient to enhance the growth performance traits, nutrients digestibility, thyroid and antioxidant system in growing Pekin ducks. In addition to, using these natural feed additives had clear favorable effect on enzymatic and microbiological profile in small intestine, without adverse effects on liver activity.