This study evaluated the effects of oregano essential oil on performance and egg quality parameters of laying hens. A total of 144 fourty-week-old H&N Super Nick laying hens were assigned to the basal control diet supplemented with 50, 100, 150, 200 and 250 mg/kg of oregano essential oil (6 treatment diets, 8 replicates, each replicate consists of 3 hens). Hens were fed experimental diets from 40 to 52 weeks of age. Water and diets were supplied ad libitum throughout the experiment. After 12 week of experiment, feed intake, egg production, feed conversion ratio, egg weight, egg mass did not differ among the treatment groups. Different application rate of oregano oil had no effects on eggshell ratio, eggshell thickness and eggshell breaking strength. The results of this study demonstrated that addition oregano essential oil to the diets had no effect on performance and eggshell quality parameters of laying hens at 40 to 52 weeks of age.