Purpose <p>How well the over 200,000 U.S. servicemembers who complete military service each year navigate the transition to civilian life may impact their later-life outcomes, with smoother transitions increasing resilience to later life stressors and leading to better long-term outcomes. The purpose of this study was to examine whether veterans who experience better military-to-civilian transitions are less vulnerable to poor mental health when faced with later stressors.</p> Methods <p>Data were drawn from a population-based sample of U.S. veterans (<i>N</i> = 9,566) who completed six biannual surveys on their health and well-being throughout the first three years following separation from military service (2016–2019), and another a year into the COVID-19 pandemic (2021). We examined veterans’ vocational, financial, and social readjustment patterns using latent growth modeling and impacts on subsequent mental health using logistic regressions.</p> Results <p>The majority of veterans reported consistently high vocational and social well-being but low financial well-being during the initial transition from service, with approximately 15% reporting declining well-being in each domain. In turn, well-being trajectories predicted veterans’ odds of experiencing probable mental health conditions (depression and anxiety) during the pandemic, even after accounting for background characteristics, prior mental health, and additional stressful/traumatic experiences. In contrast with those with consistently low well-being, those with initially low then increasing vocational, financial, and social well-being reported similar mental health as those with consistently high well-being.</p> Conclusions <p>These results underscore the importance of bolstering support for transitioning veterans and point to strategies that can be applied to improve their longer-term mental health.</p>