Carotenoids are a large class of natural antioxidants that occur in many vegetables, foods and other natural sources. To date, a large number of biological properties have been reported from carotenoids, particularly protective effects against diabetes mellitus (DM), cancer, and neurodegenerative, metabolic and cardiovascular diseases. However, recent studies including clinical evidences, have shown that carotenoids play a role in the treatment of diabetes via enhancing insulin sensitivity. They are also able to protect the body from long-term consequences of diabetes including infectious diseases, nephropathy, neuronal and eye abnormalities. In this review, we try to discuss the mechanisms behind the biological effects of carotenoids for the prevention and treatment of DM and its complications. The authors believe that carotenoids will have a prominent place in the treatment of DM and its complications in the future.