A growing body of evidence demonstrates that school-based mental health interventions have negative outcomes in at least some young people and thus are potentially harmful for these individuals. In this scoping review, we map out the empirical evidence relating to this phenomenon. We review three specific areas: the types of potential harms reported in school-based mental health interventions; the subgroups of children and adolescents at heightened risk of experiencing potential harm from school-based interventions; and the proposed explanations for these potential harms.