Key words:Broilers, Immunity, Antioxidant, Performance, ThymeThe current study aimed to determine the immune and antioxidant status, and performance of broiler chickens fed diets supplemented with thyme (Thymus vulgaris) leaves powder, as an alternative growth promoter. Therefore, a total of 120 one-day-old Cobb chicks were fed for 35 days with four experimental diets containing thyme powder (0, 5, 10 and 15 g/kg: these were designated groups Control, Thyme I, Thyme II and Thyme III, respectively). The GC-MS analysis of n-hexane extract of thyme showed the presence of isocaryophyllene (33.73%) as a major active ingredient with other antioxidant ingredients. Serum total protein and globulin content was significantly increased in thyme-supplemented chicks at the 3 rd week and significantly increased in Thyme I and III at the 5 th week. Serum albumin and creatinine content and ALT activities were non-significantly increased in the thyme-supplemented chicks at the 3 rd and 5 th weeks. Moreover, serum total cholesterol and triacylglycerol levels were significantly decreased in the thyme groups at the 3 rd and 5 th weeks. Dietary thyme supplementation for broiler was significantly improved serum IgG, IgM, INF-γ, and IL-10 levels, and muscle glutathione content, superoxide dismutase, and glutathione S-transferase with significantly reduced malondialdehyde levels. Regarding to growth performance, thyme 0.5% was non-significantly improved the final body weight, body weight gain, feed conversion ratio, and protein efficiency ratio of broiler chicks. So, these data indicated that incorporation of thyme into the broiler's diet was improved the immune status and antioxidant activities in broilers. Also, production of broilers meat with low levels of lipid peroxidation products. Corresponden ce to: * doaavet792016