Selenium is an essential element for mammals but it has not been considered as essential for higher plants. The effect of Se application on lentil grain yield, antioxidant activity, nitrogen fixation, and seed Se concentration studied. Experiments were conducted at Carrington Research and Extension Center in 2012 and 2013. Selenium fertilization increased the lentil grain yield by 5 % in 2012 and by 9 % in 2013. Selenium application increased the antioxidant activity (70 % inhibition) of lentils compared to the untreated control (61% inhibition). Percentage nitrogen derived from air was increased with Se fertilization by 17 % and 12 % in 2012 and 2013, respectively, with Se fertilization. Seed Se concentration was significantly higher in selenate treated lentils (1.4 mg/kg) compared to selenite (0.9 mg/kg) and the control (0.6 mg/kg). Overall, application of Se increased lentil grain yield, nitrogen fixation, antioxidant protection, and seed Se concentration.