We describe a case of plasma cell leukemia associated with myelofibrosis. A 60-year-old woman was admitted due to lumbago and monoclonal hypergammaglobulinemia. Peripheral blood showed about 40% of plasma-cell-like cells. A bone marrow aspiration was dry tap. The patient was diagnosed as having plasma cell leukemia with myelofibrosis by bone marrow biopsy. Plasma cell leukemia as well as myelofibrosis improved with combination chemotherapy using vincristine, pirarubicin, and dexamethasone. However, when plasma cell leukemia became resistant to chemotherapies, myelofibrosis also reappeared. This case strongly suggests the pathogenetic relationship between plasma cell leukemia and myelofibrosis.