Purpose <p>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.</p> Methods/patients <p>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.</p> Results <p>79 informal primary caregivers participated, mostly women (65%, <i>N</i> = 51), middle-aged (median 57, SD = 9), employed (54%), and spouses (58%, <i>N</i> = 46). Most had medium economic status (70%, <i>N</i> = 55), no other dependents (51%, <i>N</i> = 40), support from other caregivers (56%, <i>N</i> = 44), and good self-rated health (82%, <i>N</i> = 65). Caregiver burden affected 61% (<i>N</i> = 48), more often women (<i>p</i> = 0.049), those with high stress (<i>p</i> = 0.001), and when more people were involved in patient care (<i>p</i> = 0.048).</p> Conclusions <p>Caregiver burden is common in informal primary caregivers of patients with advanced cancer receiving palliative treatment, especially in highly stressed women.</p>