This study investigated longitudinal trajectories of stigma (i.e., enacted, anticipated, internalized, concealed); stress-sensitive mental health disorder symptoms (i.e., depression, social anxiety); and their associations across 8 annual assessments in a sample of 128 young gay and bisexual U.S. university students. All forms of stigma significantly decreased over time, while depressive symptoms remained stable and social anxiety symptoms significantly increased. Men from higher socioeconomic backgrounds experienced quicker reductions in anticipated stigma, compared to men from lower socioeconomic backgrounds. More self-described feminine men experienced quicker reductions in concealment, compared to more self-described masculine men. Enacted stigma demonstrated contemporaneous associations with depression and social anxiety across 8 years; and anticipated stigma and internalized stigma demonstrated contemporaneous associations with social anxiety across 8 years. Enacted stigma was more strongly associated with depressive symptoms among men who reported greater masculinity compared to those who reported greater femininity. Findings are discussed in terms of common developmental influences across early sexual orientation identity formation, including gay and bisexual young men’s resilience to stigma-based stress; the transition from college; and the rapidly changing social climate surrounding sexual minority individuals. Findings suggest the need for future longitudinal examinations of stigma and mental health among sexual minorities that utilize multiple age cohorts to determine the relative contribution of cohort-specific versus common maturational factors influencing the mental health of this population.