To discuss families' experiences of their interactions when a relative is admitted unexpectedly to an Australian intensive care unit.The overwhelming emotions associated with the unexpected admission of a relative to an intensive care unit are often due to the uncertainty surrounding the condition of their critically ill relative. There is limited in-depth understanding of the nature of uncertainty experienced by families in intensive care, and interventions perceived by families to minimise their uncertainty are not well documented. Furthermore, the interrelationships between factors, such as staff-family interactions and the intensive care unit environment, and its influence on families' uncertainty particularly in the context of the Australian healthcare system, are not well delineated.A grounded theory methodology was adopted for the study.Data were collected between 2009-2013, using in-depth interviews with 25 family members of 21 critically ill patients admitted to a metropolitan, tertiary-level intensive care unit in Australia.This paper describes the families experiences of heightened emotional vulnerability and uncertainty when a relative is admitted unexpectedly to the intensive care unit. Families uncertainty is directly influenced by their emotional state, the foreign environment and perceptions of being 'kept in the dark', as well as the interrelationships between these factors.Staff are offered an improved understanding of the barriers to families' ability to regain control, guided by a grounded theory of family resilience in the intensive care unit.The findings reveal in-depth understanding of families' uncertainty in intensive care. It suggests that intensive care unit staff need to focus clinical interventions on reducing factors that heighten their uncertainty, while optimising strategies that help alleviate it. Families are facilitated to move beyond feelings of helplessness and loss of control, and cope better with their situation.