<i>Objective:</i> Renal ischemia/reperfusion (I/R) injury occurs in both native and transplanted kidneys. Hyperbaric oxygen (HBO) has been shown to prevent I/R injury in different tissues. The aim of this study was to evaluate the effect of HBO on renal I/R injury in rats. <i>Materials and Methods:</i> Sprague-Dawley rats were randomly assigned to one of three groups. The Control group (n = 6) received right nephrectomy. The I/R (n = 6) and I/R+HBO groups (n = 6) received 30 min left renal ischemia followed by 24 h of reperfusion after right nephrectomy. The I/R+HBO group (n = 6) received additional HBO therapy for 60 min at 2.5 absolute atmospheres starting at the initial 15th minute of reperfusion. <i>Results:</i> In the I/R group, blood urea nitrogen (BUN) and creatinine levels increased significantly compared with the Control and I/R+HBO groups (p < 0.05). BUN and creatinine levels were similar in the Control and I/R+HBO groups. Kidney samples from I/R group rats revealed severe tubular damage and neutrophil infiltration at histopathological examination. The animals treated with HBO showed markedly improved lesions and less neutrophil infiltration compared with the I/R group (p < 0.05). <i>Conclusions:</i> HBO exhibited marked protection against I/R injury in this study as measured using BUN and creatinine levels and renal histopathology. However, further studies are needed to clarify the renoprotective effect of HBO on I/R injury.