Prior research has demonstrated that behavioral, demographic, and mental health characteristics are associated with suicide, particularly among youth and young adults. Although recent research has begun to explore developmental trajectories of suicide-related outcomes, few studies to date have extended beyond late adolescence. Understanding different trajectories of suicide-related thoughts and behaviors from adolescence through mid-adulthood has the potential to refine developmental perspectives on suicide risk and to inform prevention efforts. Using National Longitudinal Study of Adolescent to Adult Health data (n = 9421 respondents with data at all four waves), this study analyzed suicide-related outcomes across ages 12–31 years. Growth mixture modeling (GMM) was used to estimate trajectory classes for past-year suicide ideation and attempts, followed by multinomial logistic regression to explore the association between race/ethnicity and class membership. In weighted descriptive analyses, the sample was 50.0% female; it was 15.5% African American, 2.1% Asian/Pacific Islander, 12.0% Hispanic, 0.9% other, and 65.9% White. GMM results revealed three trajectory classes for ideation: sustained higher risk, sustained lower risk, and adolescent-limited risk. Two trajectory classes emerged for attempts: declining higher risk and sustained lower risk. For ideation, African Americans were less likely than Whites to be in either the sustained higher risk or the adolescent-limited risk trajectory. For attempts, African Americans had significantly lower odds than Whites and Asians/Pacific Islanders had nearly four times the odds of Whites of being in the sustained higher risk trajectory, though the latter was only marginally significant. The finding of associations between race/ethnicity and distinct patterns of suicide-related behavioral development from early adolescence into mid-adulthood suggests new directions for developmental research and provides evidence to inform future suicide prevention efforts.