Chimeric antigen receptor (CAR) T-cell therapy is an effective new treatment strategy for hematologic malignancies. The success of CAR T-cell therapy in treating leukemia and lymphoma has promoted its development for multiple myeloma (MM), and the initial results of CAR T cell therapy have been encouraging. CAR T-cell therapy target antigens that have been clinically evaluated in MM; these antigens include CD19, B cell maturation antigen (BCMA), CD38, and CD138. A barrier to the widespread use of CAR T-cell therapy is its toxicity, primarily cytokine release syndrome (CRS), and neurologic toxicity. This study reports a patient with refractory MM who also developed megakaryocyte aplastic thrombocytopenia after receiving CAR T-cell therapy; such a case or the unusual side effects involving medications are yet unreported. There are risks in using cyclosporine and other immunosuppressants that may lead to MM recurrence as the use of such substances is contradictory to previous treatments; therefore, we temporarily administered platelet infusion as supportive care. Thus far, the condition of the patient has been steady andthe patient regularly takes blood test in the hospital.