BACKGROUND: Although several chimeric antigen receptor T cells (CAR T) targeting CD19 are curative for patients with relapsed/refractory(R/R) B-cell lymphoma, but the clinical safety and efficacy of this CAR T therapy remain unclear. The risk of secondary malignancies, especially myeloid neoplasms, is of particular concern in the CAR T therapy. METHODS: A patient with R/R follicular lymphoma was diagnosed with secondary myelodysplastic syndrome (s-MDS) after CD19 CAR T therapy. We also provided a review of recently published literature concerning the risk of secondary myeloid neoplasms (SMN) following CAR T therapy. RESULTS: The patient had secondary MDS after CD19 CAR T therapy. She received active treatment for nearly one year and then she died. CONCLUSIONS: The case illustrated the onset and progression of SMN after CD19 CAR T therapy in patients with R/R B-cell lymphoma and provides useful information of this uncommon later event.