A 69-year-old man was referred to our department for a cystic tumor, 4.0 cm in diameter, in the lower portion of the right kidney, which was detected by computed tomography. The patient had been admitted to the department of surgery in our hospital for treatment of ileus caused by transverse colon cancer. With a diagnosis of cystic renal cell carcinoma. T2N0M0, in situ non-ischemic tumor enucleation was performed using a microwave tissue coagulator (Microtaze, Heiwa Electronics Industry Inc., Tokyo). The enucleation was accompanied by a defect of the renal pelvis, but it was easily repaired. The operation time was 120 minutes and blood loss was 110 cc. The histological diagnosis was renal cell carcinoma, pT2N0M0V1, expansive, alveolar type, clear cell subtype, G1 > G2. Diagnostic imaging done postoperatively showed no sign of damage to renal function. At the present time, the patient has been disease-free with interferon-alpha for 12 months and is being followed on an outpatient basis. In this report, the advantages of nephron-sparing surgery, especially in situ non-ischemic tumor enucleation using a microwave tissue coagulator for renal tumor are discussed. In particular, the technique of performing tumor enucleation with repair of the defect of renal pelvis used in this case may extend the indication of nephron-sparing surgery.