An 82-year-old man was diagnosed with synchronous non-muscle-invasive bladder cancer and left lower ureteral carcinoma. He underwent transurethral resection of the bladder tumor, followed by total left nephroureterectomy after preoperative chemotherapy with four courses of gemcitabine and carboplatin. Histopathological findings showed positive-margin carcinoma in situ. In addition, since recurrence of non-muscle-invasive bladder cancer was observed in the bladder, Bacille Calmette-Guérin intravesical infusion therapy was performed, but the cancer persisted due to treatment resistance. After that, pembrolizumab therapy was performed, and complete remission was achieved.