This article describes a phenomenological research study exploring the effect of social interaction upon mental health nurse student learning. Central to this study are ideas about Communities of Practice as described by Wenger et al. (2011). The researcher conducted two focus groups and four semi-structured interviews with mental health nurse students at various stages of their training. The study found that students understand personal progress by comparison with others and that there is a relationship between peer group membership and learning outcomes. Students interpret academic studies and theoretical knowledge in a dynamic relationship with clinical practice where successful learning depends upon careful negotiation of social boundaries. Whilst acknowledging limitations this paper concludes by tentatively suggesting some implications for future nurse education practice which recognises the socially mediated nature of learning.