This study examined associations between reactive and proactive functions of aggression and suicidal behavior in a sample of outpatient treatment seeking youth (n = 111, 60.5% male) ranging from 6 to 17 years of age (Mean age = 10.57 years). Additionally, hope was evaluated as a moderator of these associations. Child reports of measures were used to evaluate associations. When also considering the variance associated with child depressive symptoms and hope, reactive, but not proactive, aggression was uniquely associated with suicidal behavior. Moreover, hope moderated this association, such that reactive aggression was only positively associated with suicidal behavior when levels of hope were low. Findings and their implications for targeting hope with aggressive youth for the prevention of suicidal behavior are discussed.