Purpose Of the Study: (1) To identify the main predictors of the emotional state of the frail elderly at the end-of-life and that of their primary family caregivers, taking into consideration the presence/absence of significant cognitive impairment in the patient and (2) to analyse the relationship between the emotional state of the patient and that of their primary family caregiver.; Methods: Our study is cross-sectional. 85 frail elderly patients at the end-of-life and their primary family caregivers participated. Information on the following aspects was collected: (1) From the patients: Socio-demographics, Functional independence, and Cognitive and Emotional state; (2) From the caregivers: Socio-demographics, Emotional state and Overburden (according to Zarit Scale). Descriptive, correlational and linear regression analyses were computed using SPSS.; Results: The models that best predict the observed variance in the emotional state of patients (with or without significant cognitive impairment) include the same variables: functional independence of the patient and caregiver's overburden. Similarly, the models that best predict the observed variance in the emotional state of family caregivers include: cognitive state of the patient and caregiver's overburden.; Implications: The overburden of the family caregiver stands out as a key factor in the reduction of the emotional distress of frail elder patients -whether or not they present significant cognitive impairment- and that of their family caregivers. Our results suggest that reducing overburden of the family caregiver may also reduce the emotional distress of the patient and that of their family caregiver.; Copyright © 2017 Elsevier B.V. All rights reserved.