Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. The biological pattern of these tumors ranges from benign-appearing small lesions to malignant sarcomas. Only 3%-5% of GISTs are found in the duodenum. A duodenal GIST is a rare source of upper gastrointestinal bleeding. A remarkable percentage of duodenal GISTs are localized in the third and fourth part of the duodenum and may not be noticed on standard upper endoscopy. Push enteroscopy is sometimes advisable to find these lesions. Surgical resection either limited or pancreaticoduodenectomy can be the treatment of choice. In general, adjuvant therapy with imatinib has been proved to extend survival in patients with GIST.The current case, a 24-year-old male, presented with acute upper gastrointestinal bleeding from a submucosal ulcerated tumor located in the distal third part of the duodenum, 3 cm distal from the papilla of Vater. After primary care and blood transfusion in a local hospital, partial resection of the duodenum was performed as a definitive surgical therapy. Histopathology showed a GIST with a diameter of 3 cm and moderately malignant according to tumor grade, and <5 mitoses/10 high power field (HPF).