A 85-year-old man achieved complete response after a course of intravesical instillation of Bacillus Calmette Guerin (BCG) therapy for carcinoma in situ (CIS) of the bladder. Two year later, urine cytology became class III. We performed random biopsy of the bladder and split urine cytology of the bilateral upper urinary tract, but none of these examinations revealed any malignant features. After a month, he consulted orthopedics for lumbago. He was indicated to have a metastatic bone tumor, and positron emission tomography-computed tomography (PET-CT) showed a hypermetabolic mass in the prostate. A transperineal needle biopsy of the prostate revealed the urothelial carcinoma (UC). Our diagnosis was invasion of CIS of the bladder into the prostate. In such cases, we recommend a needle biopsy of the prostate in addition to a transurethral biopsy of the bladder and prostate.