In this study, the authors investigated the efficacy of the Youth-Nominated Support Team-Version 1 (YST-1), a psychoeducational social network intervention, with 289 suicidal, psychiatrically hospitalized adolescents (197 girls, 92 boys). Adolescents were randomly assigned to treatment-as-usual plus YST-1 or treatment-as-usual only. Assessments were completed pre- and postintervention (6 months). There were no main effects for YST-1 on suicide ideation or attempts, internalizing symptoms, or related functional impairment. Relative to other girls, however, those who received YST-1 reported greater decreases in self-reported suicidal ideation (actually treated analytic strategy) and significantly greater decreases in mood-related functional impairment reported by their parents (intent to treat and actually treated analytic strategies). This is the first randomized controlled clinical trial to investigate the efficacy of a social network intervention with suicidal youths.