Posttransplant lymphoproliferative disorder (PTLD) is a serious complication of solid organ transplantation. It has several clinical manifestations, including infectious mononucleosis-like syndrome, lymphadenopathy, and other organ involvement. Soft palate ulcer is a rare manifestation of PTLD. The aim of this study is to present a 17-year-old girl with liver transplantation due to metastatic liver disease. After transplantation, she presented with a painful whitish ulcerative lesion accompanied by central necrosis in the right soft palate area measuring about 3 cm×3.5 cm. Histopathologic evaluation of the lesion showed monomorphic B-cell-type PTLD. She received 6 courses of CHOP chemotherapy plus rituximab. In the follow-up, the lesion disappeared with scar formation. Therefore, PTLD has different clinical presentations and may involve any part of the body. Therefore, when an unusual oral lesion after solid organ transplantation is observed, PTLD should be considered in addition to other differential diagnoses.