In order to determine the effects of adding different levels of Satureja khuzistanica essential oilin two conventional and microcapsulated forms into the diet on performance, immune response, blood biochemical parameters and intestinal morphology of broiler chickens, an exprement was conducted using 400 Ross 308 (mixed sex) broiler chickens, in five treatments, four replicates and 20 chickens per each replicate. The expriment was done in a completely randomized design. Treatments included control (no additive), dietary containing levels of 400 and 500 mg/kg Satureja essential oil and dietary containing levels of 0.5 and 1.00 percent capsulated Satureja essential oil. Adding different levels of Satureja khuzistanica essential oil in conventional and microcapsulated forms to diet of broiler chickens had no effect on feed intake,FCR, immune response and the number of white and red blood cells. However, experimental treatments containing conventional and microcapsulatedformof Satureja essential oil caused a significant decrease in body weight of the birds relative to than the control treatment. The level of thyroid hormones (T3 and T4) and blood biochemical parameters (cholesterol, triglyceride, HDL and LDL) were not affected by the experimental treatments. Although small intestin histologhy traits like width of villi, depth of crypt and length of villi to depth of crypt ratio were not affected by the experimental treatments, the level of 0.5 percent capsulated Satureja essential oil caused a significant decrease in length to width of villi ratio (P<0/05). Acccording to the results of the present experiment, using of two common and microcapsulated Satureja essential oil forms,  have not any  effect on performance, blood biochemical parameters and immune response.