Background: The study examined the burden of caring for individuals with autism spectrum disorder (ASD) transitioning from high school and factors associated with burden derived from the Double ABCX model of family adaptation (i.e., autism symptom severity, problem behaviors, pileup life demands, personality traits, social support, cognitive appraisals, and coping strategies). In particular, we were interested in the potential association between the "big 5" personality traits and burden. Method: Participants (N = 105) were caregivers of individuals with ASD within two years preor post-graduation from high school. Results: Primary caregivers reported moderate levels of burden. As hypothesized, burden was significantly associated with both child (i.e., increased autism symptom severity and problem behaviors) and caregiver characteristics (i.e., greater neuroticism, lower levels of extraversion, conscientiousness, agreeableness, and social support, and increased use of threat appraisals and passive-avoidance coping strategies). Using multiple regression, increased child behavior problems and increased caregiver use of passive-avoidance coping were identified as independent predictors of burden. Passive-avoidance coping mediated the relationship between caregiver burden and individual personality traits (i.e., neuroticism, extraversion, conscientiousness).