Tumors of the angle of Treitz are a rare entity. Only 3%-5% of gastrointestinal stromal tumors (GISTs) occur at the level of the duodenum, and their location at the duodenojejunal junction is very uncommon. Surgery is the treatment of choice, while adjuvant medical therapy is used on the basis of the degree of radicality of the excision and the tumor's proliferative profile. These factors primarily influence the prognosis. Due to the frailty of the vascular viability of the left duodenum, which can be injured during surgery, it is generally recommended to perform digestive reconstruction at the level of the right portion of the duodenum. We here report the case of a patient with a large GIST located at the duodenojejunal junction behind the ligament of Treitz. We found reconstructive digestive anastomosis at the level of the third part of the duodenum to be a safe procedure.