Gentamicin is a potent antibiotic, effective against Gram negative bacteria. The most common adverse effect of gentamicin is nephrotoxicity. Present study was aimed to explore the protective potentials of Citrullus colocynthis against gentamicin induced nephrotoxicity due to its strong antioxidant properties. Toxic doses of gentamicin (80 mg/kg/day, i.m.) were administered alone and as co-therapy with the extract of C. colocynthis (25 mg/kg/day, p.o.). Physiological, biochemical and histological examinations were performed to compare the experimental and toxic groups (n = 6) with control group animals. Co-therapy of C. colocynthis with gentamicin protected changes in the body weight, blood urea nitrogen, creatinine clearance, proteins and lactate dehydrogenase excretions. However, a significant rise in serum creatinine and serum uric acid with fall in serum calcium and serum potassium was observed, which were significantly different from control group animals. Necrotic and ruptured tubules were also found abundantly. This study revealed that co-theapy of C. colocynthis with gentamicin for twenty one days, failed to protect renal injury associated by gentamicin in spite of its strong antioxidant properties.