Background: Caring for a person with dementia is associated with well-documented increases in burden and distress and decreases in mental health and wellbeing. Studies assessing burden in caregivers of patients with dementia and its determinants are scarce in Latin America. Objective: The main objective of this study was to assess the extent and the determinants of burden in informal primary caregivers of patients with dementia in Chile. Methods: A descriptive study was conducted using clinically validated scales to assess dementia characteristics and to measure caregiver variables. Family socio-demographic characteristics and functional status, patient functional dependency and behavioral disturbances, and caregiver psychiatric morbidity were analyzed as independent variables to determine caregiver burden. Results: Two hundred and ninety-two informal caregivers were included. There were more female (80%) than male caregivers, consisting mainly of daughters and spouses of the patients.