Introduction: The present study was designed to evaluate the therapeutic efficacy of melatonin and insulin co-administration in diabetic-induced renal injury in rats. Research design and methods: Diabetes was achieved by giving streptozotocin (15 mg/kg) for 6 consecutive days and animals having blood glucose levels above 250mg were considered as diabetic. Following the confirmation, animals were randomly divided into different experimental groups, viz group-I, group-II, group-III, group IV, group V, group VI, group VII, group VIII, and group IX. Following the completion of the experimental period, animals were sacrificed, blood was collected via retro-orbital puncture, and kidneys were harvested. Results: Diabetic rats exhibited a significant increment in biochemical indexes of renal injury including augmented levels of serum creatinine, urea, uric acid, Na+, and K+, and suppression of the activity of GPX, GR, G6PDH, and GST in the renal cortex. By examining thiobarbiturate reactive substances, GSH level and SOD and CAT activities in the renal cortex of diabetic rats it was documented that treatment with melatonin or insulin alone or in combination showed a significant ad integrum recovery of glutathione-dependent antioxidative enzymatic activities. Melatonin and insulin co-administration caused greater reductions in circulating TNF-α, TGF-β1, IL-1β, and IL-6 levels in diabetic rats whereas IL-10 levels increased, as compared to each treatment alone. Diabetic rats showed a significant increase in expression of both MT1 and MT2 melatonin receptor genes. Melatonin or insulin treatment alone or in combination resulted in significant restoration of the relative expression of both melatonin receptors in the renal cortex. Conclusion: The co-administration of exogenous melatonin and insulin abolished many of the deleterious effects of type 1 diabetes on rat renal function.