Heart failure is a growing public health problem associated with significant morbidity and mortality. Family support positively affects outcomes for the person with heart failure while also leading to caregiver burden. Registered nurses have a key role in supporting and meeting the needs of family caregivers. The overall aim was to explore the situation and needs of family caregivers to a person with heart failure, and explore requisites and ways of supporting and involving family caregivers in heart failure nursing care. Two interview studies, one web survey study and one intervention study were conducted between 2012 and 2017. A total of 22 family caregivers, eight persons with heart failure and 331 registered nurses participated in the studies. Family caregivers' daily life was characterized by worry, uncertainty and relational incongruence but salutogenic behaviours restored new strength and motivation to care. Family caregivers experienced that their caregiving was taken for granted by health care professionals. Family caregivers expressed a need for a permanent health care contact and more involvement in the planning and implementation of their near one’s health care together with health care professionals. Registered nurses acknowledged family caregivers’ burden, lack of knowledge and relational incongruence. A registered nurse was suggested as a permanent health care contact to improve continuity and security. Registered nurses neither acknowledged family caregivers as a resource nor their need for involvement. Registered nurses working in primary health care centres, in nurse-led heart failure clinics, with district nurse specialization, with education in cardiac nursing care held the most supportive attitudes toward family involvement in heart failure nursing care. Family health conversations via telephone in nurse-led heart failure clinics were found to successfully support and involve families. The conversations enhanced nurse-family relationship and relations within the family. They also provided registered nurses with new, relevant knowledge and understanding about the family as a whole. Family health conversations via telephone were feasible to both families and registered nurses, although fewer and shorter conversations were preferred by registered nurses. This thesis highlights the divergence between family caregivers’ experiences and needs, and registered nurses’ perceptions about family caregivers’ situation and attitudes toward the importance of family involvement. It adds to the knowledge on the importance to acknowledge family caregivers as a resource and to support and involve them in heart failure nursing care. One feasible and successful way is to conduct Family health conversations via telephone in nurse-led heart failure clinics.