We report an extremely rare case of primary ileal plasmacytoma accompanied by mixed low- and high-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type. The radiographic and macroscopic features of the tumor were characterized by two constricting lesions in the ileum. Histologic examination of the resected specimen showed that one constrictive lesion was plasmacytoma and the other MALT lymphoma was low and high grade. The plasmacytoma seemed to have differentiated from the MALT lymphoma.