Post-transplant lymphoproliferative disorder (PTLD) is a well recognized and potentially fatal complication after pediatric cardiac transplantation. PTLD encompasses a wide spectrum, ranging from benign hyperplasia to more aggressive lymphoma. Most cases are Epstein-Barr virus (EBV)-related B-cell tumors resulting from impaired immunity due to immunosuppressive therapy. Pediatric recipients, often seronegative for EBV at transplantation, have a greater risk for PTLD than adults. The clinical presentation of PTLD varies from isolated lymphadenopathy to systemic disease; common sites involved are gastrointestinal tract, lung or airway, and cervical lesions. Timely and accurate diagnosis based on histological examination of biopsy tissue is essential for early intervention. Immunostaining for EBV and evaluation for clonality are needed. For prophylaxis when EBV viral loads are increasing or for initial treatment of early lesions or polymorphic PTLD, a reduction in immunosuppressive treatment is a key component of therapy, but caution is needed for possible rebound allograft rejection. Chemotherapy is indicated for patients with poor response to reduced immunosuppression and for highly aggressive monomorphic PTLD. The use of rituximab in combination with chemotherapy is effective. For the time being, avoiding excessive immunosuppression is the most effective strategy for reducing the incidence of PTLD. Calcineurin inhibitor (CNI) minimization with proliferation signal inhibitors (PSIs) or conversion from a CNI to a PSI might be useful for preventing both development of PTLD and allograft rejection.