PURPOSE: Recently, there has been an increase in awareness of social stigma and mental health issues experienced by transgender individuals in South Korea. To provide quantitative evidence, we conducted a nationwide cohort study of transgender adults, first of its kind in Asia. The aim of the study is to assess the prevalence of depressive and anxiety symptoms and examine their associations with discrimination experiences among transgender adults. METHODS: We conducted a two-wave longitudinal survey of 269 Korean transgender adults, where the baseline was collected in October 2020 and the follow-up in October 2021. Experiences of discrimination in the past 12 months at follow-up were categorized accordingly: those who experienced (1) none, (2) only anti-transgender discrimination, (3) only other types of discrimination, and (4) both anti-transgender and other types of discrimination. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression scale at both waves and anxiety symptoms were measured using the Generalized Anxiety Disorder 7 only at follow-up. We used modified Poisson regression to examine the association between experiences of discrimination and mental health outcomes at follow-up and adjusted for sociodemographic characteristics and baseline depressive symptoms. RESULTS: A total of 63.9% had depressive symptoms and 47.2% had anxiety symptoms. Participants who experienced both anti-transgender and other types of discrimination had 1.38-times (95% CI 1.06-1.81) and 1.77-times (95% CI 1.16-2.70) higher prevalence of depressive and anxiety symptoms, respectively, compared to those without any experiences of discrimination. CONCLUSIONS: Interventions to lessen discrimination towards transgender individuals are needed for the promotion of mental health among transgender individuals.