This video demonstrates a Boari flap ureteroneocystostomy using laparotomy in an oncological ureteral obstruction. This technique of urinary reconstruction is used to fix lumbar ureteral defects using the tubulization of a bladder flap, allowing for the extension of the ureter towards the bladder. The success rate of ureteral reimplantation can be higher than 85% and it is used for the treatment of ureteric lesions caused by traumatic, oncological or iatrogenic injuries. Psoas hitch is the usual technique for the treatment of most distal ureteric resections. However, an additional Boari flap is required to treat longer and higher resections.