Objective: to describe the level of uncertainty in illness in family caregivers of palliative care patients and detect associations between the profile of the caregiver and the levels of uncertainty.; Method: descriptive correlational study conducted with 300 family caregivers of hospitalized patients. The sociodemographic characterization of caregiver and patient was used to assess the caregiver profile, as well as the Uncertainty in Illness scale for family caregivers. Spearman's Rho correlation test was applied to detect associations.; Results: the average score of illness uncertainty was 91.7 points. The analysis showed significant correlations between the level of uncertainty and patient dependence (r=0.18, p=0.001), symptom assessment (r=0.312, p<0.001), length of service as a caregiver (r=0.131, p=0.023), perception of support from health professionals (r=-0.16, p=0.048), family (r=-0.145, p=0.012) and religious support (r=-0.131, p=0.050).; Conclusions: there were high levels of uncertainty in caregivers about their patient's illness. These levels are associated with the health condition and symptoms of the patient who is cared for, the length of service as a caregiver and the perceived support from health professionals, family and religion.