Abstract: The present study was carried out to investigate the effects of dietary supplementation with vitamin E and stocking density on performance, thyroid function, plasma concentration of corticosterone (Cort), some blood parameters, (antibody (Ab) titers against Newcastle Disease Virus (NDV) and Avian Flu virus (AF)) and antioxidant status in broiler chickens. In all 192; 3-day-old commercial broiler chickens (cobb 500) were randomly divided into 8 treatments groups, each of which include 4 replicates. Experimental treatments consisted of a 4x2 factorial arrangement design with 4 levels of vitamin E and 2 levels of stocking density (11.90 birds m-2 as the normal stocking density or 16.66 birds m-2 as the high stocking density). Vitamin E levels were 0.0, 200, 300 and 400 mg kg-1 diet. Increasing vitamin E level in the diet did not affect Live Body Weight (LBW), Body Weight Gain (BWG), feed intake and FCR. Also, increasing vitamin E levels had no effects on T4, Total Lipids (TL), total cholesterol (Chol) and high density lipoprotein cholesterol (HDL). However, supplementing vitamin E had a significant effect on SOD, NDV and AF titers but decreasing effect on MDA. In addition, plasma Cort and LDL levels were lower at 300 mg kg-1 vitamin E supplementation but plasma Total Protein (TP) and albumin (Alb) levels were higher at 300 mg kg-1 vitamin E supplementation. The normal stocking density has significant effects on LBW, BWG, FI, Cort, TP, TL and chol compared with the high stocking density. However, stocking density did not affect FCR, T3, T4, Alb, LDL, HDL and SOD. The results of the present study show that supplementing of vitamin E at 300 mg kg-1 of diet has a positive effect on productivity, immunity and blood parameters in broiler chickens.