Background: Primary family caregivers (PFCs) in the intensive care unit (ICU) experienced stress and stress-related symptoms such as sleep disturbances and fatigue. These symptoms may cause physical and mental health problems and affect the quality of care that they provide to their care recipients. Purpose: This study explored the levels of severity of stress, sleep disturbances, and fatigue experienced by PFCs in the ICU in order to understand the associations and to explore the predictors and influencing factors in the period following the first ICU admission of their care recipients. Methods: This descriptive correlational study was based on Lazarus and Folkman's Stress-Coping theory. Four questionnaires including the Impact of Events Scale - Revised, General Sleep Disturbance Scale, Lee's Fatigue Scale, and the Norbeck Social Support Questionnaire were used to measure the psychological stress symptoms and social support received by 72 PFCs. Descriptive statistics and multiple hierarchical regression analysis were utilized for data analysis. Results: The participants suffered from high levels of event stress, poor sleep quality, and fatigue severity. However, they also received generally high levels of social support. Stress perception was found to positively associated with sleep disturbances and fatigue severity. The participants who experienced higher event stress sought additional assistance. The age and perceived event stress of PFCs were significant predictors of sleep disturbances, while perceived event stress was the only significant predictor of fatigue. Conclusions/Implications for Practice: This study provided healthcare professionals with important information to understand the psychological symptoms of PFCs. Future studies should identify the stressors of this caregiver group and explore their psychological symptoms during different hospitalization periods. Further interventions should be developed to help PFCs cope with stress and improve stress-related symptoms such as sleep quality and fatigue severity.