A 77-year-old woman was admitted due to progressive dyspnea on exertion for 2 weeks. Chest radiography showed opacification of the left hemithorax. Chest ultrasonography revealed a massive amount of pleural effusion and multiple nodular lesions on the left pleura. Pleural effusion cytology showed dispersed anaplastic cells resembling plasma cells. Bone marrow biopsy verified the diagnosis of multiple myeloma. Malignant pleural effusion is a rare manifestation of multiple myeloma. Approximately 30 cases have been reported in the English literature since 1950. We herein report 1 case and review the literature.