As health professionals in an educational setting, nurses in schools occupy a unique place in the spectrum of children's services. Yet the service is often overlooked and has been described as invisible. This paper draws on findings from a study, funded by the Scottish Government's National Programme for Improving Mental Health and Well-being, which explored the role of school nurses in promoting and supporting the mental health of children and young people. The school nursing service throughout the United Kingdom is at a pivotal point as its role is being redefined to align with moves across the National Health Service towards a public health model. This paper therefore offers a timely overview of the mental health work of school nurses, and raises key issues for future work. Interviews were conducted with 25 school nurse managers across Scotland. Interviewees claimed that the contribution of nurses in schools was distinctive, owing to the quality and consistency of relationship that they could offer, and the autonomy that the service allowed young people. However, significant challenges were reported in making this contribution, and tensions were evident in the conceptualisation of their role. The framework of resilience is used to discuss the findings on the significance of building relationships in promoting mental health. (Contains 1 note.)