question: INTRODUCTION While various surgical techniques have been reported for open and minimally invasive treatment of upper tract urothelial cancer (UTUC), the procedure of robot-assisted nephroureterectomy (NU) with bladder cuff has never been reported using only retroperitoneum without entering abdominal cavity. We developed a novel port placement and technique allowing to perform robot-assisted NU by a unique retroperitoneal approach. METHODS Between February and June 2021 patients with history of UTUC were treated by robot-assisted NU completely restricted to retroperitoneal space using a singular trocar placement and a two-step docking without relocation of the surgical robot. Patient characteristics, perioperative outcomes and short-term follow-up were prospectively analyzed. RESULTS The analysis included five patients [median age: 73 years; BMI: 27.2 kg/m2; Charlson comorbidity index 5]. All five patients had UTUC with a mean tumor size of 3.02 cm (range 0.9-6.0). UTUC was localized to distal ureter in two and to kidney in three cases. No positive surgical margins were noted for all patients with UTUC [1 low-grade and 4 high-grade]. Retroperitoneal lymphadenectomy in three patients did not reveal positive nodes. No intraoperative adverse events exceeding EAUiaiC classification ≥ 2 were observed, while median EBL was 150 ml (IQR 100-250). No patient experienced postoperative complications exceeding Clavien-Dindo classification ≥ 3a. Median hospital stay was 5.4d without any 30-d readmission. CONCLUSION We demonstrate safety and feasibility of the first entire robot-assisted retroperitoneal nephroureterectomy (RRNU) with bladder cuff. This surgical technique is easily reproducible, while surgical outcomes are similar to other established techniques.