ObjectiveRelatively few dyad‐based studies have evaluated the shared psychosocial and financial toxicity (FT) experiences of hematologic patients and their caregivers, especially those undergoing bone marrow transplantations (BMTs). This study evaluated the association of FT with health‐related quality of life (QOL) among BMT patient‐caregiver dyads.MethodsSurvey and electronic health record data were collected between April 2021 and January 2022 from BMT patients and their caregivers pre‐ (T1) and post‐intervention (T2). Thirty‐four patient‐caregiver dyads completed surveys; all dyads included a patient experiencing elevated T1 FT. The effect of the total FT score (i.e., the combination of psychological response, coping behaviors, and material conditions domain scores) on physical health, mental health, anxiety, depression and distress scores was evaluated using Actor‐Partner Interdependence Modeling (APIM).ResultsPatients and caregivers who reported lower total FT scores had better physical and mental health, and lower anxiety, depressive symptoms, distress (APIM actor effects). None of the partner effects were significant in the APIM models. Other model findings indicated that compared with caregivers, patients had lower reported physical health; mental health scores were higher, on average, for all participants at the T2 compared with T1; and members of dyads whose caregiver took time off work reported better physical health and lower depressive symptoms and distress than those whose caregiver did not.ConclusionsOur study addresses a significant gap in dyad‐based cancer FT studies; the findings underscore the need for additional research to help develop tailored dyad‐level FT interventions for improving health‐related QOL among BMT patients.