A 65-year-old man was referred to our Urology Department with a right renal tumor. He had a medical history of urothelial carcinoma of the urinary bladder, and he was treated with transurethral resection and intravesical BCG immunotherapy consisting of 6-weekly instillations at the age of 62. A CT performed 2 years before showed no recurrence or metastasis. However, recent dynamic contrast-enhanced CT showed a 1 cm dorsal renal tumor. Gradual and weak enhancing effects were suspected in the periphery of the tumor. MRI fat-saturated T2-weighted images showed slightly low signal intensity, suggesting renal cell carcinoma. The suggested differential diagnoses were a papillary renal cell carcinoma, a complicated cyst, and an angiomyolipoma. However, only the tumor periphery was stained. The finding did not seem to be typical of papillary renal cell carcinoma. After discussion with radiologists, we decided to perform a partial nephrectomy. RAPN was done through the retroperitoneal approach without renal artery clamping and renorrhaphy. The tumor was resected with margin using sharp incision and blunt dissection. During resection, white pus came out from the tumor. The operative time was 104 min, and the estimated blood loss was 10 mL. Histopathological examination revealed an epithelioid cell granuloma with necrosis of the right kidney, which were considered to be changes after BCG therapy for bladder cancer. Numerous lymphocytes and Langhans giant cells are observed. The lesion extended from the renal cortex to the peripheral fat tissue, with no evidence of fungi with periodic acid–Schiff stain or Grocott's stain or of acid-fast bacilli with Ziehl–Neelsen's stain.