Infusion of contrast agents increases osmotic load, viscosity, hypoxemia of the renal medulla and renal free radical production through post-ischemic oxidative stress. The present experimental study sought to determine whether melatonin, because of its anti-oxidant properties might have a preventive and protective role against the development of contrast-induced nephropathy (CIN). Twenty-four adult male rats were divided into four experimental groups: healthy control rats (CR), rats with CIN (CINR), rats with CIN pretreated with melatonin (CINR1M), and rats with CIN pre- and post-treated with melatonin (CINR2M). In CINR, both serum creatinine (Cr) level and fractional excretion of sodium (FE-Na) significantly increased, whereas Cr clearance decreased at post-CIN compared with pre-CIN period. Rats in CINR1M did not show any improvement in renal function. Cr clearance decreased, whereas both serum Cr level and FE-Na increased in rats pretreated with melatonin. In contrast, significant improvements were observed in CINR2M. Serum Cr and Cr clearance did not change, whereas FE-Na significantly reduced in rats pre- and post-treated with melatonin. In conclusion, the present experimental study clearly demonstrated the preventive and protective role of melatonin against the development of CIN.