Background. Post-transplant lymphoproliferative disorder (PTLD) is known as one of the most frequent post-transplant neoplastic diseases, which may lead to recipient and graft morbidity after liver transplant. Patient. A 14-year-old boy received pediatric living donor liver transplant (right living graft) 29 months ago, with etiology of biliary atresia. During 22-month follow-up after transplant, computed tomography and positron emission tomography with computed tomography scan showed a single progressive mass locating in the graft cutting surface with occlusive reconstructed middle hepatic vein (MHV). Serology was negative for Epstein-Barr virus serology. Mild fever and pneumonia did not improve after 1-week intravenous antibiotics. PTLD was considered. Results. A surgical resection was scheduled and performed in compliance with the Helsinki Congress and the Istanbul Declaration. During laparotomy, a single mass located in the reconstructed MHV from segment V to the inferior vena cava was confirmed. Postoperative immunohistochemical result showed CD 3(+), CD 20(+), CD 38(+), CD 10(-), CD 56(-), Ki-67(+, 20%-30%), Epstein-Barr virus -encoded RNA(-), and Epstein-Barr virus nuclear antigen 2(-). Polymorphic PTLD was eventually diagnosed. No recurrence or new set lesions were detected after 6-month follow-up. Conclusions. This is the first case describing PTLD may originate from reconstructed MHV after pediatric living donor liver transplant. As a life-threatening complication of liver transplant, surgical resection should be considered as a safe and feasible treatment for the single resectable mass.