Purpose of the Study: Converging evidence from large community-based samples, Internet studies, and Veterans Health Administration data suggest that transgender adults have high rates of U.S. military service. However, little is known about the role of prior military service in their mental health later in life, particularly in relation to identity stigma. In this article, we examine relationships between prior military service, identity stigma, and mental health among transgender older adults. Design and Methods: We used a subsample of transgender older adults (n = 183) from the 2014 survey of Aging with Pride: National Health, Aging, and Sexuality/Gender Study (NHAS). We employed weighted multivariate linear models to evaluate the relationships between psychological health-related quality of life (HRQOL), depressive symptomatology (Center for Epidemiological Studies Depression Scale [CES-D] scores), identity stigma, and prior military service, controlling for background characteristics. Results: Identity stigma was significantly related with higher depressive symptomatology and lower psychological HRQOL. Having a history of prior military service significantly predicted lower depressive symptomatology and higher psychological HRQOL. The relationships between psychological HRQOL, identity stigma, and prior military service were largely explained by depressive symptomatology. Prior military service significantly attenuated the relationship between identity stigma and depressive symptomatology. Implications: By identifying the role of military service in the mental health of transgender older adults, this study provides insights into how prior military service may contribute to resilience and positive mental health outcomes. Directions for future research are discussed.Keywords: Veterans, Gender identity, Resilience, Depression, Quality of life Estimating the prevalence of current and former U.S. service members who self-identify as transgender is challenging, yet important to understanding of the effects of military service in this population. The Veterans Health Administration indicates the prevalence of diagnosed gender dysphoria is five times that of prevalence estimates in the general population (Blosnich et al., 2013). Gates and Herman (2014) propose that there are more than 15,000 transgender adults currently serving in the U.S. military. The RAND Report commissioned by the U.S. Department of Defense suggests that of the more than 2.1 million active duty and reserve military personnel, between 2,150 (0.1%) and 10,790 (0.5%) are transgender (Schaefer et al., 2016). Due to the rapidly increasing aging population and the high The Gerontologist cite as : Gerontologist, 2017, Vol. 57, No. S1, S63-S71 doi:10.1093 proportion of veterans among older Americans (more than 50%; Hardy & Reyes, 2016), the number of transgender older adults with a history of military service is likely substantially increasing. In a national community-based survey, 41% of transgender older adults reported having previously serv...