This study aimed to investigate the effect of different levels of silymarin against lead induced oxidative stress in broiler chickens. Therefore, 240 broiler chickens of Ross 308 allocated to 24 experimental units in a completely randomized design with factorial 2x3 arrangements and four replicates of 10 birds. The experimental diets containing silymarin at 3 levels (0, 100, 200 mg/kg) and 2 levels of lead (0, 200 mg/kg) were fed for 6 weeks. Results of this experiment showed that supplementation of 200 mg/kg silymarin attenuated adverse effect of lead on body weight gain (BWG) and feed conversion ratio (FCR) in 42 d. Also, addition of 200 mg/kg silymarin in lead-induced oxidative stress improved carcass characteristics. In addition, supplementation of silymarin in lead-induced oxidative stress no significantly decreased blood lipid parameters (cholesterol, triglyceride, LDL). Furthermore, supplementation of 200 mg/kg silymarin significantly increased superoxide dismutase (SOD) and decreased malondealdehyde (MDA) and heterophyle /lymphocyte (H/L ratio). These results suggested that supplementation of silymarin in lead induced oxidative stress had a protective role and by improving the antioxidant system improved the performance.