Disclosing a sexual minority (e.g., lesbian, gay, or bisexual) identity to others is an ongoing process throughout life. Research shows that disclosure is stressful, and this stress is related to poorer mental health for sexual minority youth. However, there are few theoretically grounded studies examining disclosure stress and its prospective association with mental health. The current study utilizes 2 conceptualizations of sexual identity development--stage models and milestone models--to contextualize how changes in disclosure-related stress are associated with depression symptoms from adolescence into young adulthood. Data come from a sample of lesbian, gay, and bisexual youth between ages 15-24 surveyed over 3 years (N = 555; 82% youth of color; 40% bisexual; 63% free and reduced lunch; and 49% assigned female at birth). We estimated (a) parallel process models and (b) growth curve models with disclosure stress as a time-varying covariate, which were respectively informed by stage and milestone conceptualizations of sexual identity development. Results indicated that depression symptoms declined while disclosure stress increased. In the parallel process model, higher baseline disclosure stress correlated with higher baseline levels and steeper declines in depression symptoms. When disclosure stress was modeled as a time-varying covariate, it was most strongly associated with higher depression symptoms at earlier ages. Disclosure is a developmental process that confers differential risk for depression symptoms earlier in the life course, which can hinder the typical decline of depression symptoms in young adulthood. Supporting sexual minority youth when they disclose their sexual identity throughout adolescence can have long-term benefits for mental health.