The objective of our study is to research biochemically and histopathologically the effect of nimesulide on oxidative damage inflicted by ischemia-reperfusion (I/R) on the rat renal tissue. Twenty-four albino Wistar type of male rats were used for the experiment. The animals were divided into groups as: renal ischemia-reperfusion control (RIR), nimesulide + renal ischemia-reperfusion of 50 mg/kg (NRIR-50), nimesulide + renal ischemia-reperfusion of 100 mg/kg (NRIR100), and sham groups (SG). In NRIR-50 and NRIR-100 groups were given nimesulide, and RIR and SG groups were given distilled water, an hour after anesthesia. Groups, except for the SG group, 1-h-ischemia and then 6-h-reperfusion were performed. In the renal tissue of the RIR group in which the malondialdehyde (MDA), myeloperoxidase (MPO), and 8-hydroxyguanine (8-OHGua) levels were measured, the COX-1 and COX-2 activities were recorded. Nimesulide at 100 mg/kg doses reduced the oxidant parameters more significantly than 50 mg/kg doses; on the other hand, it raised the antioxidant parameters. It has been shown that 100 mg/kg doses of nimesulide prevented the renal I/R damage more significantly than a dose of 50 mg/kg, which shows that nimesulide, in clinics, could be used in the prevention of I/R damage.