Background: Over the last few decades, there has been an increase in mental health problems among adolescents, manifested as physical symptoms, such as stomach pain, headaches, feelings of anxiety, worry, stress and sleeping problems. Surveys among school nurses' have revealed that mental health work now forms a key part of their role. Although an increasing number of adolescents are suffering from mental health problems in upper-secondary schools (16-19 years), there are few studies focusing on this matter. Therefore we wanted to explore the matter from the school nurses' point of view. The aim of this study was to explore Swedish school nurses' experiences of caring for and promoting the health of students suffering from mental health problems. Methods: The present study had a descriptive design and a qualitative approach. A purposeful sample of eight (n = 8) school nurses was interviewed. Their working experience varied between 4 and 29 years. The data were analysed using content analysis. The ethical principles stipulated by the Swedish Research Council were carefully followed throughout the study. Results: Three main themes with sub-themes were found: A caring relationship as the foundation for health promotion, organizing health-promoting work and interprofessional cooperation as a prerequisite for good caring. Conclusions: The findings strengthen the evidence of the importance of the health dialogue as a tool for the school nurses to identify students with mental health problems. Creating a caring relationship with the students is a prerequisite for caring and health promotion. Further education concerning mental health and evidence-based-practice should be arranged on regular basis. More research and cooperation between different stakeholders is needed.