Aim: To provide lifeworld insights into experiences of adult children with caring responsibility for an 80+-year-old chronically ill parent with frailty. Background: Informal care is common in Nordic welfare countries; however, little is known about adult children's experience of caring responsibility in this setting. Design: A phenomenological–hermeneutic study based on Reflective Lifeworld Research. Methods: Diaries and semi-structured interviews with 12 adult children. Results: Caring responsibility is identified as “a condition of life, filled with uncertainty.” Three constituents contribute to this phenomenon: (a) balancing love, duty and reciprocity; (b) being the parent's advocate and manager; and (c) experiencing concerns and bodily strain. Conclusion: Adult children work hard to provide care and enhance the well-being of their parent. Heidegger's concept ‘Fürsorge’ may help us understand how by showing how caring responsibility means balancing different roles vis-à-vis the parent, one's own life and the health and social systems. Caring responsibility changes the relationship between parent and child.