Post-transplant lymphoproliferative disorders (PTLD) are long-term complications of immunosuppression after solid organ/bone marrow transplantation. In most cases, PTLD arises as a result of primary or reactivated Epstein-Barr virus infection in a host with impaired cellular immunity. PTLD is most often seen in the gastrointestinal tract, although it has also been reported in other organ systems, including the central nervous system and, rarely, in the head and neck. It is characterized histologically by abnormal lymphoid cell proliferation. Although many forms of PTLD do not meet all of the histologic criteria of lymphoma, they often behave clinically in a malignant fashion if left untreated. We present 3 rare cases of PTLD manifesting in the oral cavity as mucosal masses after solid organ transplantation. There are only 8 published reports of PTLD in the literature presenting as oral lesions. The clinical, pathologic, and therapeutic spectra of PTLD are discussed.