A 63-year-old man with a horse shoe kidney was evaluated after an episode of asymptomatic gross hematuria. Cystoscopy revealed bladder tumor near the right ureteral orifice, and transurethral resection demonstrated high grade pT1 urothelial carcinoma. The patient was started on intravesical BCG instillation therapy at a dose of 81 mg weekly for 8 weeks without fever. 6 months later after the final BCG treatment, CT examination demonstrated a renal hypovascular tumor in an isthmus of a horseshoe kidney. We couldn't deny malignant tumor and tumorectomy was performed. Histological examination revealed epithelioid cell granulomas and no organisms were identified by Ziehl-Neelsen or Grocott-Gomori stains for acid-fast bacilli and fungi. We reported a rare case of renal tuberculosis in an isthmus of a horseshoe kidney after BCG therapy for bladder cancer that was considered due to vesicoureteral reflux.