The objective of this study was to determine the relationship of postpartum oxidative stress and the ovarian anoestrus in the dairy cows. The study concluded that excess free radical production with elevation of the cortisol hormone might play a role in the prolongation of the postpartum anoestrus in dairy cows. These may be due to exhaustion of antioxidant system in milk production, so it was advise supplementation the dam with antioxidants during the late stage of pregnancy and in postpartum period to stimulate the normal ovarian activity and cyclicity.