PURPOSE: Assess the frequency of caregiver burden among patients with advanced cancer receiving palliative anticancer treatment. Compare characteristics of those who show caregiver burden versus those who do not. METHODS/PATIENTS: This is a cross-sectional study in two university hospital oncology departments. Caregivers completed the Reduced Zarit Burden Interview and Emotional Distress Thermometer. Data were analyzed to identify factors associated with caregiver burden. RESULTS: 79 informal primary caregivers participated, mostly women (65%, N = 51), middle-aged (median 57, SD = 9), employed (54%), and spouses (58%, N = 46). Most had medium economic status (70%, N = 55), no other dependents (51%, N = 40), support from other caregivers (56%, N = 44), and good self-rated health (82%, N = 65). Caregiver burden affected 61% (N = 48), more often women (p = 0.049), those with high stress (p = 0.001), and when more people were involved in patient care (p = 0.048). CONCLUSIONS: Caregiver burden is common in informal primary caregivers of patients with advanced cancer receiving palliative treatment, especially in highly stressed women.