Suicide is a leading cause of death among adolescents in many industrialized countries. We report evidence from a mediation model linking greater youth activity engagement, spanning behavioral and psychological components, with lower suicide risk through five hypothesized intrapersonal and interpersonal mediating factors. Self-report survey data (15 percent French, 85 percent English) were gathered from a community sample of 5,015 Canadian adolescents participating in a mental health promotion program. Youth (M age = 15.77, SD = 1.42, 50 percent female) were from two urban centers in southern Ontario, Canada. Youth engagement (youth's most important type of activity, frequency of involvement, and psychological engagement), suicide risk predictive factors (self-esteem, current concerns, depressive symptoms, coping ability, and connections with others), and suicide risk (ideation and attempts) were assessed. Consistent with the hypothesized mediation model, enjoyment and stress in youth's most important activity and various activity types were associated with the various hypothesized suicide risk predictive factors, which in turn were related to suicide risk. Implications for conceptualizations of youth engagement as a multidimensional construct and for suicide risk prevention efforts are discussed. Figure, tables, and references (Published Abstract)