Most of the malignant tumors of the pancreas are adenocarcinomas arising from the ductal epithelium. Primary leiomyosarcoma of the pancreas, even though it is the most common sarcoma of the pancreas, is very rare. We present a case of leiomyosarcoma of the pancreas, probably primary, with metastases to the stomach, lymph nodes, and abdominal wall. A 52-year-old woman visited the hospital with vague right upper abdominal pain and weigh loss of 6 kg for 2 months. The radiological and endoscopic examination revealed that she had a large heterogeneous mass, 11 cm in size, in the pancreatic body and tail, a 4 cm-sized mass in the paraaortic area, and a 3 cm-sized polypoid mass in the stomach. Histologically, they were all similar to one another and composed of markedly pleomorphic cells. Immunohistochemical and electron microscopic studies showed definite smooth muscle differentiation of the tumor cells. Two months later, the patient underwent an excision of a new 3 cm mass in the right lower abdominal wall, showing features of well differentiated leiomyosarcoma.