Background: The role of caregivers is important for the successful support of left ventricular assist device (LVAD) patients. We aimed to (1) evaluate quality of life (QoL) of caregivers pre-and post-LVAD implant and (2) identify factors associated with caregivers' QoL.; Methods: The caregivers' QoL was assessed with the Short Form-8 before implant, at 3 and 6 months after LVAD implantation. The physical and mental component summary (PCS and MCS) scores were calculated. Caregiver burden was evaluated using the 8-item Zarit Caregiver Burden Interview.; Results: Data were collected from LVAD patients as bridge-to-transplant and their family caregivers in Japan. No significant changes were found in caregivers' PCS scores during the follow-up (before 52.7±7.1; at 3 months 49.7±6.5, and at 6 months 50.7±6.4, n=20). Compared with the scores before implant (38.9±9.3), the caregivers' MCS scores improved after LVAD implantation at 3 months (44.2±7.7; p=0.03) and at 6 months (46.2±7.4, p=0.003), but they were still lower than those of the Japanese general population (p<0.01). In multiple regression analysis at 3 months (n=40), caregivers' lower PCS scores were associated with older patient age [standard partial regression coefficients (sβ)=-0.36, p=0.02] and caregiver unemployment (sβ=0.30, p=0.04), whereas being female (sβ=-0.26, p=0.03), being the patient's spouse (sβ=-0.23, p=0.03), and having a mild to moderate caregiving burden (sβ=-0.63, p<0.001) were associated with lower MCS scores among caregivers.; Conclusions: LVAD implantation improves caregivers' mental QoL. Since caregivers' MCS scores are lower than the general population, it is important to identify family caregivers at risk for low QoL and reduce their caregiving burden.