Extramedullary involvement of the endocardium is rare in multiple myeloma. Here we describe a case of multiple myeloma (plasma cell) with extramedullary plasmablastic transformation and endocardial involvement, which resulted in partial superior vena cava obstruction. We also conducted a literature review and summary analysis of space-occupying lesions in the heart in 12 patients with multiple myeloma (including the current case) in the last 10 years. Echocardiography is the preferred radiologic examination method for diagnosis and follow-up in multiple myeloma, and surgical resection is effective for alleviating symptoms.