BACKGROUND Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal tumor, which can develop in nearly all anatomical locations. It is extremely rare in the duodenum and only seven cases have been reported previously.These lesions are of unknown etiology characterized by proliferation of myofibroblastic with an inflammatory infiltrate. It is considered a tumor of borderline malignancy. OBJECTIVE We report the first case described of IMT located isolated in the third duodenal portion, which develops as a massive intestinal bleeding in a 14 years old girl. RESULTS Complete surgical excision was successful and after 36 months of follow up the patient is asymptomatic.