Remarkably little is known regarding the temporal course of adolescent suicidal ideation and behavior, the prediction of suicidal attempts from changes in suicidal ideation, or the prediction of suicidal attempts after accounting for suicidal ideation as a predictor. A sample of 143 adolescents 12-15 years old was assessed during psychiatric inpatient hospitalization and again at 3, 6, 9, 15, and 18 months postdischarge through a series of structured interviews and parent- and adolescent-reported instruments. Symptoms of depression, posttraumatic stress disorder, externalizing psychopathology, hopelessness, and engagement in several forms of self-injurious/suicidal behaviors (i.e., suicide threats/gestures, plans, nonsuicidal self-injury [NSSI]) were assessed. Latent growth curve analyses revealed a period of suicidal ideation remission between baseline and 6 months following discharge, as well as a subtle period of suicidal ideation reemergence between 9 and 18 months postdischarge. Changes in suicidal ideation predicted suicide attempts. After accounting for the effects of suicidal ideation, baseline suicide threats/gestures also predicted future suicide attempts. Higher adolescent-reported depressive symptoms, lower parent-reported externalizing symptoms, and higher frequencies of NSSI predicted weaker suicidal ideation remission slopes. Findings underscore the need for more longitudinal research on the course of adolescent suicidality.