OBJECTIVE The present study was designed to determine the levels of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and non-enzymatic antioxidants (vitamins C and E) in aqueous humor of primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) patients. METHODS In this study, aqueous humor of POAG (n = 30) and PACG (n = 30) patients was obtained. For control, aqueous humor of 30 age-matched cataract patients (n = 30) was collected. Activities of antioxidant enzymes and non-enzymatic antioxidants levels were measured spectrophotometrically. RESULTS A significant increase in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities was found in aqueous humor of POAG and PACG patients as compared to cataract patients (p < 0.001). No significant changes were observed in catalase activity. The levels of vitamins C and E were significantly lower in the aqueous humor of POAG and PACG as compared to cataract patients (p < 0.001). CONCLUSIONS These results suggest that a significant increase in oxidative stress may play a role in the pathogenesis of POAG and PACG. Determination of oxidative stress in aqueous humor may help in understanding the course of this disease, and oxidative damage might be a relevant target for both prevention and therapy.