Key Points• Childhood HSCT survivors suffer from a higher burden of severe/life-threatening conditions compared to conventional therapy survivors.• Seven percent of HSCT survivors exhibit frailty phenotype at early age, placing them at higher risk for early mortality. vs 4.6%, P , .001) conditions, and frail health (7.1% vs 1.6%, P , .001) were higher after HSCT than conventional therapy. These results underscore the need for clinical follow-up and provide data to guide the development of prevention and/or intervention strategies for this vulnerable population.