Mechanistic and law-enforcement interventions aimed at preventing truancy do not account for the social and psychological issues associated with the phenomenon. In fact, the approach may even negatively impact adolescents' well-being and mental health. Funded by the EU, the project 'Work together to stop truancy among youth' (WE-STAY) explored the relationship between truancy and mental health. Researchers collected relevant epidemiological data, with lifestyle, family attitudes and coping strategies among the comprehensive range of topics under investigation. Just over 11 000 adolescents were recruited from study sites in Estonia, Germany, Israel, Italy, Romania and Spain. Three school-based intervention programmes were implemented. Adolescents were randomised across four intervention arms: professional screening (TRUANCY-SCREEN), awareness of truancy and mental health problems (TRUANCY-AWARE), combination of the professional screening and awareness interventions (TRUANCY-COMBINE), and a mechanistic control arm for truancy (TRUANCY-MIC). The outcomes of all interventions were evaluated from a multidisciplinary perspective that also took into account social and psychological aspects. After one month of interventions, pupils across the entire sample showed a significant decrease in school refusal drives and significant improvements were observed with regard to well-being. Follow-up at 12 months showed that 52.2 % of the originally identified truant students had become non-truant. For all pupils, the highest rates of non-truancy at follow-up were observed in the 'Mechanistic' intervention. However, considering only truant pupils at baseline, the highest rates of non-truancy at follow-up were seen in the 'Combined' intervention. As such, a combination of interventions was shown to be able to significantly help truant pupils. Project members then recommended best practices and effective, culturally adjusted models for preventing truancy and promoting adolescent mental health in different European countries. WE-STAY outcomes thus underline the benefits of introducing approaches to promoting mental health that make school safe and offer interventions for pupils at risk. This not only serves to reduce truancy rates, but also has an impact on mental health, a key determinant of general health, both in the short and long term.