Background: Ureteropelvic junction obstruction (UPJO) is one of the most common causes of upper urinary tract obstruction in the pediatric age group. Surgical repair is indicated in cases with significantly impaired renal drainage or progressive deterioration of renal function. Objective: The aim of the current study was to identify the outcome of pyeloplasty in children with split renal function (SRF) less than 10%. Patients and methods: This observational retrospective analytical study carried out on 28 children ≤ 16 years with split renal function of ipsilateral kidney £ 10% in the Urology Department, Faculty of Medicine, Zagazig University. The study was conducted during the period from 2013 to 2019. All patients were subjected at the time of pyeloplasty to clinical assessment, laboratory investigation & imaging study. Results: GFR, SRF were highly significantly increased in post-operative follow up renogram at 6 months and 12 months. Antero-posterior diameter (APD) and parenchymal thickness were highly significantly reduced at 6 month post-operative follow up ultrasound. There were a highly significant improvement in degree of hydronephrosis from grades III & IV to I & II. Conclusion: Our data confirm emerging evidence that the outcome and prognosis of Anderson-Hynes pyeloplasty (AHP) in children with severely impaired renal function is good that show highly significant improvement of renal function postoperative.