Two rare cases of mesenteric fibromatosis are presented, The first patient had a right upper quadrant mass and colicky abdominal pain. The tumor originated from the mesentery of the colon and it infiltrated the gallbladder, cystic duct, and the liver. The second patient had severe hematemesis and melena, The origin of the tumor, which infiltrated 3/4 part of the stomach, the gastrohepatic ligament, the first part of the duodenum, and the liver could not be determined. In the first patient, partial colectomy and cholecystectomy were performed and the liver lesion was completely excised. The second patient underwent subtotal gastrectomy and left lobectomy of the liver. The first part of the duodenum was excised. Gastrojejunostomy was performed. No recurrence was recorded in either patients during 16 and 13 months follow-up, respectively. In this report, diagnostic aids, differential diagnosis and treatment of this rare disease are discussed.