Objective: Informal family caregivers provide critical support for patients receiving chimeric antigen receptor (CAR) T‐cell therapy. However, caregivers' experiences are largely unstudied. This study examined quality of life (QOL; physical functioning, pain, fatigue, anxiety, and depression), caregiving burden, and treatment‐related distress in caregivers in the first 6 months after CAR T‐cell therapy, when caregivers were expected to be most involved in providing care. Relationships between patients' clinical course and caregiver outcomes were also explored.