There has been a growing concern regarding the adverse events including hematological malignancies which occurring in the later stages following CAR-T immunotherapy. Here, we presented a case of secondary MDS/AML following CAR-T immunotherapy in our center. This refractory/relapsed MM patient who received systematic treatment including chemotherapy and targeted drug as well as autologous stem cell transplantation was developed into MDS and AML especially after BCMA CAR-T immunotherapy, and even allogeneic hematopoietic stem cell transplantation could not save the very poor prognosis. Further meta-analysis also demonstrated the considerable heterogeneity through the total studies CD19 and BCMA CAR-T subgroups. In conclusion, it is imperative that long-term and close monitoring for patients undergoing CAR-T immunotherapy, with particular attention to the potential development of hematological malignancies.