It is now well established that virtually all abiotic and biotic stresses induce or involve oxidative stress to some degree and the ability of plants to control oxidant levels is highly correlated with stress tolerance. Recently, the role of Selenium (Se) as an antioxidant has generated a wide interest in it. In trace amounts, Se is an essential micronutrient and has important benefits for animal and human nutrition although it has not been confirmed to be an essential micronutrient in higher plants. Selenium has been shown to exert a positive effect on crop growth and stress tolerance at low concentrations. However, the specific physiological mechanisms that underlie the positive effects of Se in plants have not been clearly elucidated. There is a wealth of evidence that low concentrations of Se enhance the growth of plants and improve antioxidative capacity of plants either by acting as antioxidant directly or by increasing the activities of antioxidant enzymes and bring out the tolerance under stressful condition. In contrast at high concentrations, Se acts as a pro-oxidant and leads to drastic reduction in yield. In this study we reviewed available literature regarding the possible regulatory role of Se in the various physiological processes of plants as well as its protective role under abiotic stress condition.