Purpose We assessed sexual orientation-related patterns in the 1-year longitudinal course (i.e., onset, remittance, persistence) and severity of suicidality. Method Data were obtained from a prospective, population-based cohort representing nearly 2.4 million Swedish young adults. Results A higher proportion of sexual minorities remitted (14.6%) compared to heterosexuals (9.5%). However, over twice as many sexual minorities (35.1%) experienced persistent suicidality as heterosexuals (15.0%). Plurisexual (e.g., bisexual, pansexual) young adults and sexual minorities aged 17–25 were at greatest risk for persistent and more severe suicidality. Conclusion Findings call for the identification of sexual orientation-related predictors of chronic suicidality to inform responsive clinical interventions.