There is international concern about the prevalence and severity of mental health difficulties and the impact such difficulties have upon individuals, families, communities and societies. Policy makers identify schools as strategic settings for promoting students' positive mental health, such as through the explicit teaching of social and emotional skills. Promoting students' mental health requires teachers to possess particular types of subject-matter knowledge, pedagogical knowledge, and knowledge of learners and their characteristics. However, mental health promotion is not typically addressed in pre-or in-service teacher education, thus raising questions about teachers' capabilities to enact policy directives for mental health promotion in schools. This paper reports a questionnaire study of 1029 Australian and Maltese teachers' perspectives about their capabilities for mental health promotion. Multilevel modelling showed significant response variations between teachers and between schools on 11 outcome factors. Maltese teachers' responses were significantly lower than Australian teachers on three outcome factors, namely, Knowledge, Teaching Resources and providing Parenting Support. Differences were also apparent between teachers of secondary and primary students, and between male and female teachers. Years of teaching experience did not show significant effects, highlighting that mental health promotion is a new area of professional learning for teachers. This study indicates that policy directives that situate mental health promotion initiatives in educational settings must be accompanied by opportunities for teachers and schools to build their capabilities in this relatively new domain of school and teacher responsibility. Our participating teachers have reported on issues of international concern, indicating that further attention to the capabilities of teachers and schools for mental health promotion in diverse cultural settings is warranted.