Background and Methodology: Gentamicin is a broad-spectrum antibiotic with restricted application in man and stock due to its side effects such as Nephrotoxicity and autotoxicity. Cinnamon bark has antioxidant properties. This is the first study on the protective effects of the hydroalcoholic extract of cinnamon on gentamicin-induced nephrotoxicity.Methods and Materials: Thirty-six mature female Wistar rats were divided into six equal groups. The control group did not receive any solvents or medicines. The experimental group I received Gentamicin with the daily dose of 80 mg/kg through intraperitoneal injection, and the experimental group II the daily 200 mg/kg gavage dose of hydroalcoholic extract of cinnamon. The experimental groups III, IV, and V were given the daily dose of 80 mg/kg of Gentamicin through intraperitoneal injection together with 50, 100, and 200 milligrams of cinnamon extract, respectively, by gavage for 21 days. Results: Serum uric acid concentration in the experimental group I increased significantly compared to the control group at the 5% probability level, and urea and creatinine concentrations in the experimental groups I and III showed a significant increase compared to the control group at the 1% probability level. Conclusions: Cinnamon extract was able to protect rats against Gentamicin-induced nephrotoxicity due to its contents of phenolic compounds and of other antioxidant substances.