Though common, postoperative hydronephrosis (POHN) following ureteroneocystostomy raises concern for an underlying obstruction. We aimed to determine the clinical significance of POHN following open (OUR) or robotic (RALUR) ureteral reimplantation.We retrospectively reviewed pediatric patients who underwent ureteral reimplantation for vesicoureteral reflux (VUR) from 2008 to 2019 by a single surgeon. Baseline characteristics, operative outcomes, and trends in POHN were assessed. POHN was defined as new onset hydronephrosis or exacerbation of pre existing hydronephrosis. Renal ultrasounds were performed 1, 4, and 12 months postoperatively. Voiding cystourethrograms were performed 4 months postoperatively. Surgical experience for RALUR cases was defined as number of ureters operated over time.Altogether, 93 patients (127 ureters) underwent RALUR and 19 patients (26 ureters) underwent OUR. POHN was found in 27.6% and 30.8% of ureters after RALUR and OUR, respectively. Rate and time to POHN resolution for RALUR (91.4%, 112 days) and OUR (75%, 211 days) were statistically similar. Odds of POHN after RALUR were directly related with preoperative VUR grade (Range OR: 2.82[2.26-3.52]) and surgical experience (Range OR: 8.88[7.16-11.02]). Surgical experience was inversely related with odds of VUR recurrence (Range OR: 0.41[0.32-0.54]). Rates of VUR resolution were comparable for OUR and RALUR patients. No patient required additional intervention for POHN.Incidence and resolution rate of POHN after OUR and RALUR were similar. Higher VUR grades were associated with increased odds of POHN after RALUR. Increasing RALUR experience improved VUR resolution rate but increased odds of POHN. Surgical success rates were similar for RALUR and OUR.II.