Objective. Phosphodiesterase (PDE) 5 inhibitor is reported to have renoprotective effects, however, its mechanisms are unknown. In this study, we investigated the effects of a PDE5 inhibitor, tadalafil, on two renal dysfunction model. Materials and Methods. 1. CKD model. We used Dahl salt-sensitive rats, which cause hypertension and CKD by high salt diet. They were divided into 4 groups, normal salt, high salt, tadalafil 1 mg/kg and 10 mg/kg treatment. 2. Nephrotic syndrome model. Adriamycin(ADR) induced nephrotic model was used. We divided into 3 groups, control, ADR, and ADR+tadalafil 10 mg/kg. We evaluated kidney function and tissues in both models. Results. 1. CKD model. High salt induced renal dysfunction and hypertension. Tadalafil 10 mg/kg treatment prevented renal dysfunction and hypertension. Tadalafil 1 mg/kg treatment also prevented kidney dysfunction, but not hypertension. Histopathological analysis revealed that tadalafil treatment attenuated glomerular injury. 2. Nephrotic syndrome model. ADR injection induced high urinary protein. Two and 4 weeks of tadalafil treatment attenuated proteinuria. Conclusion. This study suggested that tadalafil is effective both CKD and nephrotic syndrome.