Suicidal thoughts and actions have typically been studied from an eventsbased perspective. Some emerging studies, however, have begun to examine suicide and related behaviors through a longitudinal perspective, specifically focusing on establishing trajectories of suicidal behavior. In general, this work produces three-class trajectories of suicide attempts among adolescents, including groups such as: (1) no or low suicidal behavior; (2) moderate suicidal behavior; and (3) high suicidal behavior. Less is known about potential trajectory patterns of suicidal ideation associated with later stages of the life course. Moreover, identifying a low-, moderate-, and high-risk group does not inform the developmental processes that create time-varying risks for suicidal thoughts and attempts. Using data from Add Health, we estimate growth mixture models to explore suicidal ideation trajectories from early adolescence to early adulthood and explore how trajectories inform the link between suicidal ideation and attempts. Our results are among the first to indicate that there are four developmental trajectories associated with suicidal ideation including low-risk, high-risk, adolescent- limited, and adult-onset trajectories of suicidal ideation. Additionally, we find that suicide attempts were more likely among those in high-risk and adult-onset trajectories, compared to those in low-risk trajectories. Considering these findings identify specific time periods in the life course that are associated with suicidal ideation and attempts, our research uncovers another clear opportunity for intentional intervention efforts within the life course. To this end, prevention implications and suggestions for future research are discussed.