The aim of the present work was to study the effect of melatonin on renal function and ultrastructure of aged rats. Twenty two Albino rats of almost equal weight (275-335 g) and age (18 months) were treated with melatonin at the rate of 10 mg/kg on alternative day for 12 weeks. The treatment resulted in significant increase in the levels of total protein, albumin, and a significant decrease in serum levels of creatinine, blood urea nitrogen (BUN), nitric oxide (NO) and a significant improvement in hematological parameters. Level of reduced glutathione (GSH) and activity of catalase (CA) in kidney homogenate increased significantly and there was a significant decrease in kidney level of malanondialdehyde (MDA) and nitric oxide. Melatonin also caused a significant decrease in serum level of sodium. Histological examination of the treated kidneys revealed intact filtration slit membrane and proximal tubules with normal mitochondria having clear cristae, clear cell junctions and normally arranged apical microvilli. Also the distal tubules showed improvement after melatonin treatment indicated by normal mitochondria with clear cristae, improvement of the basal laminae and clear basal infoldings. In conclusion, the findings of the present study revealed the anti-oxidant, anti-inflammatory and protective potential of melatonin, recommending the usage of melatonin to reduce age related deterioration in renal ultrastructure and function.