To identify scalable interventions for improving sexual minority mental health and health-risk behavior, this study tested the efficacy of two self-guided online writing interventions-expressive writing and self-affirmation. To reach sexual minority young adults living in high-stigma, low-resource settings, we developed and tested these interventions in Appalachian Tennessee.In consultation with sexual minority young adults (n = 10) and stakeholders (n = 10) living in Appalachian Tennessee, we adapted these two writing interventions that we then delivered to 108 local sexual minority young adults (Mage = 23.68, SD = 3.11). Participants, representing diverse sexual and gender identities and socioeconomic backgrounds, were randomly assigned to participate in a 3-session expressive writing intervention, self-affirmation intervention, or neutral control. Participants completed mental health and health-risk behavior measures at baseline, postintervention, and 3-month follow-up.Compared to the neutral control, expressive writing exerted 3-month improvements in depressive symptoms (d = 0.48) and general psychological distress (d = 0.36) whereas self-affirmation exerted improvement in suicidal ideation (d = 0.62) and drug abuse (d = 0.59). Participants who were exposed to greater contextual minority stressors common in rural regions (i.e., discrimination and victimization) experienced significantly greater 3-month reductions in depression from expressive writing and self-affirmation compared to control. Those who experienced greater discrimination also experienced significantly greater 3-month reductions in suicidality from self-affirmation compared to control.Brief writing interventions exert significant impact on the mental health of young adult sexual minorities, especially those exposed to minority stress. Future research can consider strategies for population-level implementation, especially in high-stigma, low-resource settings. (PsycInfo Database Record (c) 2020 APA, all rights reserved).