We decided to report a case of gastrointestinal stromal tumor of the small intestine in a patient with neurofibromatosis type 1 because of the increase of its incidence as shown in the literature, also, by its revelation; its occurrence in a picture of acute peritonitis due to the rupture of the tumor. These tumors, commonly called by their English acronym GIST (Gastro-Intestinal Stromal Tumors), found in people with neurofibromatosis type 1 generally occur in the small intestine and are often multiple.