Abstract: OBJECTIVE: Many post-9/11 veterans struggle with psychological symptoms as they transition to civilian life. Adverse childhood experiences, combat exposure, and deployment characteristics are factors associated with symptoms. This study examined changes in the predictive power of these factors over the first 3 years of the military-to-civilian transition among post-9/11 veterans. METHODS: This was a longitudinal survey study in which six waves of data were collected over 3 years. RESULTS: The associations between combat, ACEs, deployment characteristics, and psychological symptoms were complex, not static, not always linear, and differed between male and female veterans. The number of deployments was associated with fewer psychological symptoms at baseline for both genders. For males, longer deployments at baseline predicted worse mental health, while more deployments were associated with improving mental health over time. CONCLUSION: Temporal explorations of veteran mental health are needed to gain insights into how and when psychological problems develop and change over time. Veterans need a robust support network to prevent mental health problems as they transition to civilian life.