Introduction: Mid-to-proximal ureteral strictures pose a surgical challenge that historically required ileal ureter substitution, downward nephropexy, or renal autotransplantation. Ureteral reconstruction techniques involving buccal mucosa or appendix have gained traction with success rates approaching 90%. In this video we describe surgical technique for a robotic-assisted augmented roof ureteroplasty using an appendiceal onlay flap. Methods: Our patient is a 45 year old male with recurrent impacted ureteral stones requiring multiple right-sided interventions including ureteroscopy with laser lithotripsy, ureteral dilation, and laser incision of ureteral stricture. Despite adequate treatment of his stone disease, he had deterioration of his renal split function with worsening right hydroureteronephrosis to the level of the mid-to-proximal ureter consistent with failed endoscopic management of his stricture. We proceeded with simultaneous endoscopic evaluation and robotic repair with plan for either ureteroureterostomy or augmented roof ureteroplasty using buccal mucosa or an appendiceal flap. Results: Ureteroscopy and retrograde pyelogram revealed a 2-3cm near-obliterative stricture in the mid-to-proximal ureter. The ureteroscope was left in situ and the patient was placed in the modified flank position to allow concurrent endoscopic access during reconstruction. The right colon was reflected revealing significant scar tissue overlying the ureter. With the ureteroscope in situ, we utilized firefly imaging to aid in our dissection. The ureter was spatulated and mucosa of the diseased segment of ureter excised in a non-transecting manner. The mucosal edges of the posterior ureter were re-approximated with the ureteral backing left in place. The appendix was harvested on its mesentery, spatulated, and interposed in a pro-peristaltic fashion. A tension-free anastomosis was performed between ureteral mucosa and the open appendix flap. A JJ stent was placed under direct vision and ICG green was used to evaluate blood supply to the margins of the ureter and the appendix flap. The stent was removed 6 weeks postoperatively, and on 3-month follow-up imaging he had resolution of his right hydroureteronephrosis and has had no further episodes of stone formation, infections, or flank pain with 8-month followup. Conclusions: Augmented roof ureteroplasty with appendiceal onlay is a valuable tool in the urologists arsenal of reconstructive techniques. Use of intraoperative ureteroscopy with firefly imaging can aid in delineating anatomy during difficult ureteral dissections. SOURCE OF Funding: NA