Ischemia/reperfusion (I/R) may through overt H₂O₂-induced pathophysiologic mechanisms lead to renal dysfunction. We explore whether catalase (CAT) protein overexpression by adenoviral CAT gene (Adv-CAT) transfection may improve ischemia/reperfusion-induced renal dysfunction. We augmented renal CAT expression by intrarenal arterial Adv-CAT administration with renal venous clamping in avertin-anesthetized female Wistar rats. After Adv-CAT transfection, we examined the CAT expression, location and effects on blood urea nitrogen (BUN) and urinary tubular injury biomarkers by biochemical assays, microcirculation by a laser perfusion imager, renal H₂O₂ amount by a chemiluminescent analyzer and molecular mechanisms including cytosolic cytochrome C leakage, apoptosis, autophagy and phospho- Akt (p-Akt)/phospho-endothelial nitric oxide (p-eNOS)/nitric oxide (NO) signaling by western blotting, immunohistochemistry and immunofluorescence. Adv-CAT enhanced 2.6-fold renal CAT protein expression primarily located in the proximal and distal tubules and renal vessels. Ischemia/reperfusion increased cytosolic cytochrome C leakage, renal H₂O₂-dependent level, autophagic Beclin-1/Atg5-Atg12/LC3 II expression, apoptotic Bax/Bcl-2/caspase 3/poly-(ADP-ribose)-polymerase fragments (PARP) expression and terminal deoxynucleotidyl transferasemediated nick-end labeling (TUNEL) stains and BUN and urinary glutathione S-transferase (GST) levels leading to proximal tubular injury. Ischemia/reperfusion also decreased renal microvascular blood flow associated with the inhibited renal expression of p-Akt and p-eNOS and NO production. Adv-CAT significantly improved the reduction in renal microvascular blood flow, reduced ischemia/reperfusion-enhanced oxidative stress, Beclin-1/Atg5-Atg12/LC3 II-meidated autophagy, Bax/Bcl-2/caspase 3/PARP-mediated apoptotic signaling, TUNEL stains, urinary GST level, and restored the p-Akt/p-eNOS/NO signaling in the kidney. Treatment of phosphatidylinositol 3-kinase inhibitors, wortmannin and LY294002, deleted Adv-CAT-induced p-Akt/p-eNOS/NO protective signaling. In conclusion, our results suggest Adv-CAT gene transfer counteracts H₂O₂-induced ischemia/reperfusion injury through preserving p-Akt/p-eNOS/NO pathway in the rat kidney.