Background: Family caregivers of persons with dementia often experience a negative impact on their health. More studies based on nursing theories are needed to improve the provision of care. Aims: To describe the care provided by family caregivers of persons with dementia and the impact on their health, as well as to analyse how personal variables of caregivers are related to care tasks and their health impact. Methods: Multi-centric cross-sectional prospective study conducted on a sample of 423 primary family caregivers of persons with dementia from Spain. Data were collected through ICUB97-R questionnaire (January–April 2019), based on the fourteen needs of Virginia Henderson's Nursing Model. Data was analysed through one-way analysis of variance and Student's t-test. Results: The caregiver profile was a middle-aged married woman without higher education living with the cared person, predominantly her mother. The most frequently provided care corresponded to “nutrition” and “movement” needs. Lack of free time, modifications on leisure activities, reduced sleep or rest and disruption of family life emerged as the greatest repercussions on the caregiver's health. The age of the caregiver and time caring showed differences on impact of care and care tasks, respectively. Conclusion: The identification of the types of care provided, the health impact of caring and the variables affecting the family caregiver's vulnerability is essential to develop effective individualised nursing care plans, including health education interventions to improve the quality of life of both caregivers and persons cared for.