No studies have examined the impact of personality traits on mental health among caregivers of individuals with severe brain injury. Therefore, the purpose of the current study was to construct linear growth models to examine whether the personality traits of family members of individuals with severe brain injury could predict the trajectories of their own mental health-related quality of life (HRQoL), anxiety, and depression beginning in a neurointensive care unit through 1 year after injury. Danish family members of individuals with severe brain injury (n = 52) completed the Short Form-36 assessing mental HRQoL (vitality, social functioning, role limitations-emotional, mental health), anxiety, and depression across 5 time points during the 1st year after injury. The measure of personality was administered 3 months after the patients' discharge. All mental HRQoL, anxiety, and depression variables improved significantly over time. Caregivers who were less neurotic and less conscientious had higher vitality, social functioning, and mental health over time, whereas caregivers who were more agreeable had higher social functioning over time. Caregivers with lower neuroticism had lower anxiety and depression over time, as well as a more accelerated decrease in anxiety and depression. Caregivers' personality traits were strongly associated over time with mental HRQoL, anxiety, and depression, with neuroticism being especially important for trajectories of anxiety and depression. These results suggest that personality assessments for caregivers of individuals with severe brain injury could help identify those most at risk for poor mental health over the course of rehabilitation. (PsycINFO Database Record