Gastro-intestinal stromal tumors (GISTs) of the appendix are a rare entity. To date, only eight cases has been described in the literature, most of which have been of the benign type. We report a new case of an appendiceal GIST in a 75-year-old man. The tumor was discovered when the patient presented with an acute appendiceacal peritonitis. Preoperative diagnosis of appendiceal GIST was rarely done as tumors were usually associated with appendicitis-like symptoms.