Here, we present 3 cases of hematologic toxicity manifested as refractory thrombocytopenia with platelet autoantibodies positive and plasma thrombopoietin (TPO) concentration elevated after bispecific CAR-T cell therapy in relapsed/refractory (R/R) MM patients who were successfully treated with standard therapy of immune thrombocytopenia (ITP). The gene discussed is TPO; the disease is autoimmune thrombocytopenic purpura.