Background: Earlier end‐of‐life communication is critical for people with heart failure given the uncertainty and high‐risk of mortality in illness. Despite this, end‐of‐life communication is uncommon in heart failure. Left unaddressed, lack of end‐of‐life discussions can lead to discordant care at the end of life. Objective: This study explores patients' and caregivers' understanding of illness, experiences of uncertainty, and perceptions of end‐of‐life discussions in advanced illness. Design: Interpretive descriptive qualitative study of older adults with heart failure and family caregivers. Fourteen semi‐structured interviews were conducted with 19 participants in Ontario, Canada. Interviews were transcribed verbatim and content analysis was used to analyse the data. Main results: Understanding of illness was shaped by participants' illness‐related experiences (e.g. symptoms, hospitalizations and self‐care routines) and the ability to adapt to challenges of illness. Participants were knowledgeable of heart failure management, and yet, were limited in their understanding of the consequences of illness. Participants adapted to the challenges of illness which appeared to influence their perception of overall health. Uncertainty reflected participants' inability to connect manifestations of heart failure as part of the progression of illness towards the end of life. Most participants had not engaged in prior end‐of‐life discussions. Conclusion: Detailed knowledge of heart failure management does not necessarily translate to an understanding of the consequences of illness. The ability to adapt to illness‐related challenges may delay older adults and family caregivers from engaging in end‐of‐life discussions. Future research is needed to examine the impact of addressing the consequences of illness in facilitating earlier end‐of‐life communication.