Objectives: In intensive care units, there is a high incidence of delirium, which relates to the risk of complications. Engagement of relatives is an acknowledged part of handling delirium, but knowledge of relatives’ perspectives is lacking. Aim: To explore relatives’ experiences of delirium in the critically ill patient admitted to an intensive care unit. Research design: A qualitative design with a phenomenological approach. Semi-structured interviews with eleven relatives of critically ill patients who had delirium during admission to the intensive care unit. Setting: An intensive care unit in Denmark. Findings: Three categories emerged: ‘Delirium is not the main concern’, ‘Communication with health-care professionals is crucial’, and ‘Delirium impacts on relatives’. Relatives had a lack of knowledge of delirium. Symptoms of delirium were thought of as a natural consequence of critical illness and seemed to be a secondary problem. Health-care professionals did not talk about delirium and information was requested. Delirium and the manifestation of it was experienced in different ways and brought different ways of coping. Conclusion: Findings give a new insight into relatives’ experience of delirium in the intensive care unit. Relatives need more information to better understand delirium. Future research must investigate the potential in helping relatives to cope with delirium, to the benefit of both patient and relatives.