The stress literature suggests that coping strategies are implicated in mental health outcomes. However, the longitudinal relationship between coping strategies and mental health in the autistic adult population has not yet been examined. This 2-year longitudinal study examined the predictive role of both baseline and change in coping strategy use over time (i.e., an increase or decrease) on anxiety, depression, and well-being after 2-years in 87 autistic adults aged 16 to 80 years. Controlling for baseline mental health, both baseline and increase in disengagement coping strategies (e.g., denial, self-blame) predicted higher anxiety and depression, and lower well-being, while an increase in engagement coping strategies (e.g., problem solving, acceptance) predicted higher well-being. These findings extend the current coping literature in autistic adults, offering insight into mental health support and intervention options.