Purpose - The purpose of this article is to present a German adaptation of the Australian programme MindMatters for school mental health promotion in secondary schools. Design/methodology/approach - As well as other methods, the external evaluation consisted of a questionnaire-based pre-post-design (at one year interval of measurement; n=633 teachers and 4,019 students). Findings - Teachers felt more positive about their schools, and felt under less pressure. The concepts of students, teachers and parents about working and living in schools became more similar (including an increase of parents' and students' suggestions for improving school-life). Students felt that the level of promotion of social competence and the clarity of behaviour codes had improved, although the reported increase was small. There was some evidence that participation in MindMatters decreased student learning and motivation. Research limitations/implications - On the whole, the recorded effects, however, were minimal (probably due to the lapse between the times of data collection and politically influenced, structural changes in schools that slowed down the implementation of MindMatters). Future research should focus on a long-term evaluation of MindMatters. Practical limitations - Since the effect of the programme was influenced by the participation in school specific teacher training and the affiliation to school health promotion networks the reported results stress the importance of teacher training for "MindMatters-schools. Originality/value - The article illustrates that MindMatters would appear to promote some aspects of mental health in schools under specific circumstances. © Emerald Group Publishing Limited.