Objective: The most common cause of urinary obstruction is ureteropelvic junction (UPJ) obstruction. In short stenosis, a dismembered pyeloplasty is performed, but for long segment stenosis, the procedure is not well defined. We present the reverse flap ureteroplasty method, which we prepared from the pelvis for use in long segment UPJ obstruction. Methods: Between 2007 and 2016, we operated on 6 cases (4 males, 2 females) with an age range of 2-6 months. After reaching the UPJ region, depending on the length of the long segment obstruction, a flap measuring 25-35 mm in length was prepared from the pelvis so that its width would be 10-12 mm on the pelvis side and 10 mm in the distal portion. It was then reversed and tubularized with an absorbable suture over a 10-French nelaton catheter. The end of this ureter and the end of the distal ureter were spatulated and anastomosed. A double J and minivac drain were used in each case. Results: There were no complications in the postoperative period of all our patients. They were all discharged with good health. Follow-up with renal ultrasonography showed that the anteroposterior diameters were decreased and that parenchymal thicknesses had returned to normal. Secondary stenosis, flap necrosis, and retraction did not develop. Conclusion: Because the blood supply of the pelvis is increased in patients with UPJ obstruction, a reverse flap of adequate length with preserved blood supply can be achieved and tubularized. We suggest that this method will be appropriate for the treatment of long segment UPJ obstruction.