Background: Pelvi Ureteric Junction Obstruction (PUJO) is defined as an obstruction to the free flow of urine from the renal pelvis to the proximal ureter1. It is the most common cause of obstructive uropathy in the paediatric age group. Aims: To check for improvement in renal function following Anderson Hynes pyeloplasty for congenital PUJ obstruction and to find out at what age should a child be operated for best improvement in renal functions. Material and Methods: A total of 20 patients undergoing Anderson Hynes Pyeloplasty were included after they satisfied the inclusion and exclusion criteria. Results: In this study it was observed that post Anderson Hynes pyeloplasty, a total of 60% children showed improvement in renal functions, in 30% there was no change in renal function while 10% showed deterioration in renal functions, requiring re-operation. The improvement was statistically significant Mean eGFR in cases improved from 32.25 to 38.5 mL/min/1.73 m2 after Anderson Hynes pyeloplasty. The improvement was statistically significant Mean renal functions in cases improved from 29.05% to 33.7% after Anderson Hynes pyeloplasty. No complications were reported in 85% of the cases after Anderson Hynes pyeloplasty. UTI developed in 2 cases (10%) while pyonephrosis was seen in 1 case (5%). Conclusion: Anderson Hynes Pyeloplasty is an effective treatment for congenital Pelvi Ureteric Junction obstruction in pediatric population. In this study it was observed that the earlier we operate the better is the improvement in function.