Numerous studies have implicated oxidative stress in the development of complications of diabetes. During hyperglycemia, production of oxidant agents such as reactive oxygen species and reactive nitrogen species increases. This process, along with a decrease in the activity of antioxidant enzymes, induces oxidative stress in the body. This redox imbalance causes damage to vital biomolecules such as proteins, lipids and DNA and results in the generation of harmful products for the body. Mechanisms associated with the creation of oxidative stress conditions and subsequently complications of diabetes are explained through several pathways such as flux through the polyol pathway, intracellular production of advanced glycation end products precursors, protein kinase-C activation, and increased activities of the hexosamine pathway. On the other hand, the study of polymorphism in the antioxidant enzymes genes indicates that some of the gene polymorphisms reduce the antioxidant power of the enzymes. This article aims to review various studies to demonstrate the effect of oxidative stress on the pathogenesis of diabetes and the positive role of antioxidants on diabetic complications.