Pleural effusion is an uncommon manifestation of multiple myeloma. Several mechanisms have been proposed for the development of pleural effusion in multiple myeloma, and most of them are benign. We report a patient with IgG-λ multiple myeloma with bilateral malignant pleural effusions and cutaneous involvement. She initially presented with massive left-sided malignant pleural effusion, and shortly thereafter, she developed right-sided malignant pleural effusion. Even though aggressive chemotherapy was administered, she died 10 weeks after diagnosis. Our observation in this case was consistent with that of other reports, in that the presentation of malignant pleural effusion indicates an advanced stage and a very poor prognosis for patients with multiple myeloma. Further investigations on malignant plasma cell biology and the explicit mechanisms of malignant pleural effusion in multiple myeloma are needed in order to improve the management and outcome of this malignancy.