The use of extracorporeal life support (ECLS) as ultimate salvage therapy for hematopoietic stem cell transplant recipients remains controversial among oncologists and critical care specialists. Prognosis is poor, particularly after allogeneic transplantation, and literature to guide clinical decision-making is scarce. Our report describes successful ECLS in a pediatric patient undergoing allogeneic hematopoietic stem cell transplantation, who developed acute respiratory failure during severe neutropenia, followed by immediate neutrophil engraftment. This unique case highlights periengraftment respiratory failure as a possible patient subgroup that could benefit from ECLS; and illustrates that the distinct etiologies of respiratory failure and the patients' immune status deserve closer consideration in future studies evaluating ECLS in this high-risk population.