In Norway, new national guidelines for school service emphasize the importance of establishing structured collaboration with schools. Nevertheless, few studies have explored the characteristics of such collaboration. The purpose of the present study is to explore how principals, teachers, and school nurses collaborate and to identify barriers and facilitators of structured collaboration. The study is based on 46 qualitative interviews conducted in five Norwegian municipalities in 2018 and 2019. The results reveal that school nurses are highly valued among the school staff but collaborations between teachers and school nurses varied both within and between schools, often for arbitrary reasons such as personal relations and office locations at schools. Personal relationships built over time as well as regular meetings, seemed to foster stronger collaboration, while discontinuity in personnel, recruitment difficulties, and sick and maternity leaves were frequently reported factors that seemed to have negative impacts on collaboration.