Robotic-assisted laparoscopic pyeloplasty is increasingly being used in children. This prospective case series demonstrates the feasibility and safety of day surgery in children undergoing retroperitoneal robot-assisted laparoscopic pyeloplasty, obviating the need for routine inpatient care. Excellent results can be achieved by careful patient selection, a clear clinical pathway, and a dedicated and experienced team. Robot-assisted pyeloplasty is the most frequently performed robotic procedure in children. A retroperitoneal approach limits surgical trauma and avoids peritoneal irritation. This led to the establishment of the criteria for day surgery (DS) and a related clinical care pathway. To assess the feasibility and safety of DS in children undergoing retroperitoneal robot-assisted laparoscopic pyeloplasty (R-RALP). We performed a bicentric prospective study (NCT03274050) over 2 yr involving the two major paediatric urology teaching hospitals in Paris. A clinical pathway and a prospective research protocol were specifically established. DS in selected children undergoing R-RALP. The primary outcomes were DS failure, 30-d complications, and readmission rates. The secondary outcomes included preoperative characteristics, perioperative parameters, and surgical outcomes. Quantitative variables were expressed as medians with interquartile ranges. Thirty-two children fulfilled specific inclusion criteria and were consecutively selected for DS following R-RALP. The median patient age was 7.6 yr (4.1–11.8) and weight 25 kg (14–45). The median console time was 137 min (108–167). There were no intraoperative complications or conversions. Six children were kept under observation overnight and discharged the following day due to persistent pain (n = 3), parental anxiety (n = 2), or a prolonged procedure (n = 1). The median duration of hospital stay of the 26 children in the DS setting was 12.7 h (12.2–13.2). During the 30-d period, there were four emergency room visits (15%) resulting in two patients requiring readmission (8%): one for febrile urinary tract infection (Clavien-Dindo II) and one child with no JJ stent for urinoma (Clavien-Dindo IIIb). Radiological studies confirmed improvement in dilatation for all cases with no recurrence (median follow-up: 15 mo). This prospective case series is the first to demonstrate the feasibility and safety of DS in children undergoing R-RALP, obviating the need for routine inpatient care. Excellent results can be achieved by careful patient selection, a clear clinical pathway, and a dedicated team. Further evaluation is warranted to assess the cost effectiveness. This study shows that day surgery after robotic pyeloplasty is both safe and effective in selected children.