Pediatric solid organ and hematopoietic stem cell transplant recipients paradoxically experience accelerated immune aging despite chronological youth, establishing a paradigm with profound implications for cancer risk and long-term outcomes. This comprehensive review synthesizes current evidence demonstrating how transplantation-related factors, anti-thymocyte globulin-mediated T cell depletion, cytomegalovirus reactivation, chronic immunosuppression, and thymic dysfunction, induce premature imm