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. Methods: Caregivers completed measures examining QOL and burden before patients' CAR T‐cell therapy and at days 90 and 180. Treatment‐related distress was assessed at days 90 and 180. Patients' clinical variables were extracted from medical charts. Change in outcomes was assessed using means and 99% confidence intervals. Association of change in outcomes with patient clinical variables was assessed with backward elimination analysis. Results: A total of 99 caregivers (mean age 59, 73% female) provided data. Regarding QOL, pain was significantly higher than population norms at baseline but improved by day 180 (p < .01). Conversely, anxiety worsened over time (p < .01). Caregiver burden and treatment‐related distress did not change over time. Worsening caregiver depression by day 180 was associated with lower patient baseline performance status (p < .01). Worse caregiver treatment‐related distress at day 180 was associated with lower performance status, intensive care unit admission, and lack of disease response at day 90 (ps < 0.01). Conclusions: Some CAR T‐cell therapy caregivers experience pain, anxiety, and burden, which may be associated patients' health status. Further research is warranted regarding the experience of CAR T‐cell therapy caregivers.