Recurrence of urothelial carcinoma in a patient with solitary kidney is always a clinical challenge. In the immune checkpoint inhibitor era, neoadjuvant immunotherapy in combination with the Yang-Monti technique might be a good option for the patient with a high-risk tumor when kidney-sparing surgery for renal function preservation is desired. We report the case of a 74-year-old man with solitary kidney who was diagnosed with recurrence of urothelial carcinoma in the right ureter. He was initially deemed unfit for segmental resection of the ureter. Neoadjuvant immunotherapy with tislelizumab was performed in this patient with a partial response to urothelial carcinoma. He underwent segmental resection of the ureter with negative margins, and the ureteral defect was bridged by modified ileal replacement, which is the Yang-Monti technique. This patient has remained disease-free with adequate kidney function for longer than 18 months.