Background: Long-term care of a relative with a disability is associated with negative consequences on the caregiver's mental health. Therefore, investigating how some personality traits, such as resilience, protect caregivers with dysfunctional personality traits from caregiving stress is necessary. This study examines the moderating role of resilience in the relationship between caregiver's personality dysfunction and care stress. Methods: A total of 224 family caregivers of children and adults with developmental disabilities participated in this cross-sectional research. They completed self-report measures of resilience, personality dysfunction, and care stress. Results: The results show that medium and high levels of resilience protect familial caregivers from the adverse effects of personality dysfunction on stress. The relationship is maintained for three of the five dysfunctional personality traits (antagonism, disinhibition, and psychoticism). Conclusions: From a theoretical point of view, the results show the contribution of the dimensional personality model to the study of caregiving stress. From a practical standpoint, the results can be used to optimise the resilience of familial caregivers, providing them with tools to take better care of their relatives.