Purpose: The purpose of this paper is to investigate the process and learning outcomes of peer collaboration in a Danish health developmental project in school health nursing. The paper explores how peer collaboration influences the school nurses' collaborative learning and competence development. Design/methodology/approach: The article is based on data from a three-year health educational development project at primary schools in Denmark. These data are observations from 12 reflective workshops with school nurses, two questionnaire surveys, and five focus group interviews with five of the six sub-projects after the project was over. In the workshops, the questionnaire surveys and the focus group interviews the school nurses were asked to reflect on the developmental process, their collaboration, own and mutual pedagogical competence development. Findings: Systematic peer collaboration between school nurses qualifies their learning and ability to reflect on practice, their communication with colleagues and children, and the development of new and innovative approaches to school health nursing. The introduction of peer collaboration, however, takes time and energy and it can be a challenge to introduce peer collaboration into a working culture in which school nurses traditionally work alone under prominent work and time pressures. Research limitations/implications: The study is explorative. Further research could explore the connection between collaborative learning among school nurses and the development of their competences in school health nursing. Practical implications: The paper outlines how and why collaboration among school nurses should be introduced in a more systematic way into school health nursing. Originality/value: The paper investigates the connection between informal educational activities for SNs and possible learning outcomes for practice. Specifically, the paper looks into different ways in which SNs collaborate and the findings contribute to new understandings of how SNs' practice can be organised in order to stimulate school nurses' participation and collaborative learning and increase the quality of school health nursing. (Contains 2 tables and 1 note.)