A 51-year-old man visited our hospital because of fever in 2003. With the discovery of the presence of a chest wall tumor, pleural effusion and M-protein, and increased plasma cells in the bone marrow, a diagnosis of multiple myeloma was established. Since the effect of combination chemotherapy followed by tandem auto-PBSCT lasted only one year, thalidomide and dexamethasone administration was started in November 2004. However, three months later, his lower limbs became swollen. Elevation of fibrin degradation product (FDP) and computed tomography findings suggested deep vein thrombosis and pulmonary embolism. With heparin and warfarin, these thromboses disappeared. Furthermore, chemotherapy strategies in addition to thalidomide were safely performed with anti-coagulation therapy. As thalidomide has become an accepted component in therapeutic strategies for multiple myeloma, careful attention must be paid to the prevention of thrombosis.