Background: Spirituality can give meaning to life, providing support and guidance in complex situations. Despite its importance in palliative care, the role of spirituality for family caregivers of patients under exclusive palliative care has not received enough attention in the literature. We aimed to address the correlation between spirituality and the emotional burden of family members of patients under exclusive palliative care. Methods: This transversal study was conducted in a tertiary private teaching hospital, in Saõ Paulo, Brazil. The study comprised family members of patients receiving palliative care exclusively. Only one caregiver who cared for the patient for at least 2 months was invited to participate. Family members answered the following questionnaires: WHOQOL spirituality, religiousness and personal beliefs (SRPB), Zarit Burden Interview (ZBI) and Self-Reporting Questionnaire (SRQ-20). They were excluded if patients were residing in a Long Stay Institution. Continuous variables were expressed by median and quartiles and analyzed with the Kruskal-Wallis test with Muller-Dunn post-test adjusted by Bonferroni or with the Mann-Whitney test for two groups. We used multivariable linear regression to identify independent predictors of caregiver burden. Results: A total of 178 family members were interviewed in a median of 8 [4-13.25] days after patient admission. Almost 40% of families presented high score of burden. Faith and Meaning in Life were the facets that scored the highest, with a median of 4.50 [4.00-5.00] for both facets. There was an inverse correlation between Zarit score and all of the WHOQOL-SRPB facets, indicating that the lower the spirituality, the greater the emotional burden. Inner peace was the strongest protective factor associated with burden. Conclusions: Psycho-socio-spiritual interaction can improve the coping ability of family caregivers of patients under exclusive palliative care, addressing a critical gap in the provision of holistic palliative care services.