Theories suggest that adolescents exposed to suicide attempts and/or deaths are at higher risk of attempting suicide, themselves. However, research findings have been mixed, with most studies not accounting for psychiatric vulnerability. We examined past psychiatric diagnosis as a moderator of the association between lifetime exposure to suicide attempts and/or deaths and adolescents’ suicide attempts. Adolescents (N = 518; 60% female; 45% White), ages 12–21, reported on prior suicide ideation and attempts, and mood, anxiety, and substance use disorders at baseline. Suicide attempts since baseline and exposure to suicidal behaviors were assessed 4–6 years later. Lifetime exposure to family suicide attempts and/or suicide deaths, but not to suicidal behaviors of peers/friends or others, was associated with a suicide attempt at follow-up among those with prior psychiatric disorders. Psychologically vulnerable adolescents may require additional support after exposure to suicidal behaviors of a family member to reduce their risk of attempting suicide.