Parkinson's disease (PD) is a neurodegenerative disorder that imposes an important burden upon the patient's caregiver. This study aims at assessing caregiver burden (CB) and analyzing its relationship with sociodemographic, emotional, and functional factors, as well as health-related quality of life (HRQoL). The following measures were applied to 80 patients with PD: the Hospital Anxiety and Depression Scale (HADS); the EuroQoL (for HRQoL); and PD-specific measures (Hoehn and Yahr staging and SCOPA-Motor ADL subscale). Patients' main caregivers completed the HADS, SF-36, EuroQoL, and Zarit CB Inventory (ZCBI). The ZCBI was found to be a valid and reliable measure in the context of PD. There was a significant association between CB and caregivers' HRQoL (r = -0.29 to -0.64). Mental aspects of caregivers' HRQoL and burden were affected by disability and disease severity. The presence of caregivers' depression had a significant negative effect on both CB and HRQoL. The main predictors of CB were caregivers' psychological well-being, patients' mood and clinical aspects of PD (disability and severity), and HRQoL of patients and caregivers. This study underscores the need to consider the impact of PD on caregivers' well-being.