Purpose to describe a new technique of complex ureteral reconstruction using a free peritoneal graft. Methods Between 2006 and 2021 we treated 11 patients with long complex ureteral strictures involving the middle ureter in 9 cases and the proximal ureter in 2 cases. Stricture length ranged from 3 to 12 cm ( mean 7 cm). Three cases were secondary to retroperitoneal fibrosis after vascular surgery in 2 cases and to Ormond disease in 1 case; 4 cases followed an extensive resection for large intra-ureteral masses, 3 cases were secondary to repeated endoscopic procedures for urinary stones and 1 case followed repeated pyeloplasty. After a longitudinal ureteral incision, a free peritoneal flap was harvested from nearby healthy peritoneum and fixed as an onlay-patch with running suture to the remaining ureteral plate after placement of a ureteral catheter. The ureter was finally wrapped with omentum. Results Follow-up has ranged from 12 to 122 months (mean 61.6 months). Seven patients were free from recurrence after 12, 18, 60, 78, 98, 99 and 122 months ( mean 69.5 months), without dilatation of the upper urinary tract and normal renal function. Four patients had a recurrence: in 1 patient the recurrence was detected after 60 months without symptoms and with mild hydronephrosis with no need for surgery. In 1 patient with Ormond disease, the recurrence occurred 6 months after the procedure without symptoms with involvement of the distal part of the 10 cm of treated ureter: a resection of the stenotic segment with psoas- hitch was performed. In the 2 other patients an obstruction below the reconstructed segment with hydronephrosis occurred 3 and 6 months after the procedure without impairment of renal function. No further surgery was performed in these patients. The limitation of this study is the small sample series, due to the high selective indications. Conclusions This technique allows the preservation of any remaining vascular supply of the ureter and can be a feasible and useful alternative to nephrectomy, ileal ureter, uretero-uretero-stomy and auto- transplantation in highly selected cases.