Pralatrexate(PDX)has been approved for the treatment of relapsed/refractory peripheral T-cell lymphoma(PTCL), including angioimmunoblastic T-cell lymphoma(AITL). Oral mucositis is the most common and severe adverse effect of PDX that often leads to dose reduction or omission. Herein, we report a 65-year-old man with AITL, who received PDX treatment after a second relapse. This drug was effective; however, the adverse effects, such as oral mucositis, were severe. Therefore, leucovorin(LV)was administered to prevent the adverse effect, resulting in continuation of the PDX treatment for 8 months. LV administration minimizes adverse effects for patients receiving high-dose methotrexate. However, the optimal dose and schedule of LV in PDX treatment has not yet been established. In the future, clinical trials on the use of LV for PDX-induced oral mucositis are needed.