This study aimed to determine the protective effects of Quercetin against 5-Fluorouracil (5-FU)-induced nephrotoxicity in rats. In this study, forty male adult rats weighing approximately 200-250 g, were used and the rats were randomly divided into five groups. According to the experimental protocol, Quercetin and 5-FU were administered to the rats, and at the end of the experimental study, intracardiac blood samples from the rats were taken under anesthesia and decapitated. Urea, creatinine, and blood urea nitrogen (BUN) values in serum samples were analyzed in an autoanalyzer. Malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx) interleukin-33 (IL-33), aquaporin-1 (AQP-1), and Nephrin parameters in kidney tissues were analyzed by commercial ELISA kits. In addition, kidney tissues were subjected to histopathological evaluation by Mallory's triple staining modified by Crossman. Serum urea, creatinine, and BUN levels were significantly increased in the 5-FU group compared to the control, Quercetin100+5-FU, and the Quercetin100 groups. Quercetin had antioxidant activity against 5-FU-induced renal oxidative stress. Also, 5-FU stimulated inflammation by increasing renal IL-33 levels and Quercetin inhibited these increases. AQP-1 and Nephrin levels were not different among the experimental groups. Especially high dose of Quercetin prevented histopathological changes caused by 5-FU. As a result of this study, it was determined that Quercetin significantly prevented 5-FU-induced nephrotoxicity in rats.