Aims and objectives: To investigate attitudes towards family involvement in care among a broad sample of Danish nurses from all sectors and healthcare settings. Background: Evidence suggests that nurses hold both supportive and less supportive attitudes about involvement of family members in the care of patients, and the existing findings are limited to specific healthcare contexts. Design: A cross-sectional study adhering to the Strengthening the Reporting of Observational Studies in Epidemiology for reporting observational studies. Methods: Using snowball sampling, the Families' Importance in Nursing Care-Nurses' Attitudes questionnaire was initially administered to a broad, convenience sample of Danish registered nurses through social media: Facebook interest groups and the homepage of the Danish Family Nursing Association. These nurses were encouraged to send the invitation to participate in their network of nursing colleagues. Complete data sets from 1,720 nurses were available for analysis. Results: In general, the nurses considered the family as important in patient care. Nurses who held master's and doctorate degrees scored significantly higher than nurses with a basic nursing education. Nurses who had had experience with illness within their own families tended to score higher on the family as a conversational partner subscale than those without this experience. Nurses with the longest engagement within hospital settings scored significantly lower than those with the longest engagement within primary health care and/or psychiatry. Conclusions: Families are considered important in nursing care. Younger nurses with a basic education, short-term engagement at a hospital and no experiences with illness within their own families were predictors of less supportive attitudes towards including the family in nursing care. Relevance to clinical practice: Clinical leaders and managers should promote education on the importance of active family involvement in patient care in clinical practice and undergraduate education. More focus on collaboration with families in the hospital setting is needed.