BackgroundThe healthcare costs of patients who receive hematopoietic stem cell transplantation (HSCT) are substantial. At the same time, the increasing use of pediatric HSCT leaves more caregivers of pediatric HSCT recipients at risk for financial burden—an understudied area of research.MethodsFinancial burden experienced by caregivers of recipients who received autologous or allogeneic transplants was assessed using an explanatory mixed‐methods design including a one‐time survey and semi‐structured interviews. Financial burden was assessed through an adapted COmprehensive Score for financial Toxicity (COST) as well as questions about the types of out‐of‐pocket costs and cost‐coping behaviors. Chi‐squared or Fisher's exact tests were used to assess differences in costs incurred and coping behaviors by financial toxicity and financial toxicity by demographic factors. Interviews were audio recorded, transcribed, and analyzed using directed content analysis.ResultsOf 99 survey participants, 64% experienced high financial toxicity (COST 22). Caregivers with high financial toxicity were more likely to report costs related to transportation and diet. High financial toxicity was associated with nearly all cost‐coping behaviors (e.g., borrowed money). High financial toxicity was also associated with increased use of hospital financial support and transportation assistance. Qualitative analysis resulted in four categories that were integrated with quantitative findings: (1) care‐related out‐of‐pocket costs incurred, (2) cost‐coping behaviors, (3) financial support resources used, and (4) multilevel recommendations for reducing financial burden.ConclusionsConsidering the substantial, long‐term financial burden among pediatric HSCT patients and their caregivers, this population would benefit from adapted and tailored financial burden interventions.