The thymus gland possesses the ability to regrow in children leading to a newly developed anterior mediastinal mass. This condition may represent a rebound phenomenon during recovery from a stressful event such as post-chemotherapy and hence was described as RTH. RTH after LT has not been well documented. We are reporting an infant with BA who underwent LT and presented with a symptomless anterior mediastinal mass, detected on follow-up imaging 6 months thereafter. Surgical partial excision was performed to rule out other differential diagnoses of a solid mass in the anterior mediastinum of an infant particularly lymphoma-that may arise as post-transplant lymphoproliferative disorder-and teratoma, as well as the other aggressive lesions such as thymoma and thymic carcinoma. The final pathological analysis revealed true thymic hyperplasia, consistent with RTH. The diagnosis of RTH should be considered for a child presenting by anterior mediastinal mass after LT.