Background: Family members of patients admitted to the intensive care unit must tolerate high levels of stress, making them emotionally and physically vulnerable. However, little is known about the kinds of stress family members may experience. Objective: To explore perceived stress in the families of patients admitted to the intensive care unit. Methods: This qualitative content analysis study involved 23 family members of patients admitted to intensive care units. Participants were drawn from family members of patients hospitalized in intensive care units of 3 public and 2 private hospitals. Data were collected through semistructured interviews. Results: Three themes emerged from the data: "distrust," "repeated stress exposure," and "a whirlpool of persistent negative emotional-physical state." The first theme had 2 categories: "fearful mindset" and "negative beliefs about professional caregivers." The second theme also had 2 categories: "fear of the future" and "sustained accumulation of tensions." The third theme had 3 categories: "impaired mental health," "impaired physical health," and "impaired family function." Conclusions: The findings of this study may help critical care nurses better understand the nature and sources of family stresses during a patient's intensive care unit stay. Supervisory nurses should alert their staff to these issues so that family care programs can address them, thereby reducing family members' risk of posttraumatic stress disorder and post–intensive care syndrome-family.