Recent years have seen an increasing emphasis on the role of teachers in promoting and supporting student mental health. It is thus important to understand how teachers' attitudes towards mental health impacts the efficacy of school mental health programs. The aim of this paper was to evaluate, based on a comprehensive review of existing literature, the relationship between teachers' attitudes and the success of school-based mental health interventions. Results indicated that teachers' attitudes towards mental health is a critical moderator of the success of related programs in schools. When teachers are supportive of, engaged in, and understand the importance of, mental health programs, students are more likely to participate in these programs and experience positive outcomes. The specific type of efforts that should be made to educate teachers about the importance of mental health and to provide them with the tools and resources necessary to effectively support student mental health in the classroom are discussed. The paper also highlights the importance of careful selection in terms of the mental health initiatives introduced within schools, and how this choice may impact teacher attitudes.