BackgroundThe provision of peer support as a component of mental health care, including the employment of Peer Workers (consumer-providers) by mental health service organisations, is increasingly common internationally. Peer support is strongly advocated as a strategy in a number of UK health and social care policies. Approaches to employing Peer Workers are proliferating. There is evidence to suggest that Peer Worker-based interventions reduce psychiatric inpatient admission and increase service user (consumer) empowerment. In this paper we seek to address a gap in the empirical literature in understanding the organisational challenges and benefits of introducing Peer Worker roles into mental health service teams.MethodsWe report the secondary analysis of qualitative interview data from service users, Peer Workers, non-peer staff and managers of three innovative interventions in a study about mental health self-care. Relevant data was extracted from interviews with 41 participants and subjected to analysis using Grounded Theory techniques. Organisational research literature on role adoption framed the analysis.ResultsPeer Workers were highly valued by mental health teams and service users. Non-peer team members and managers worked hard to introduce Peer Workers into teams. Our cases were projects in development and there was learning from the evolutionary process: in the absence of formal recruitment processes for Peer Workers, differences in expectations of the Peer Worker role can emerge at the selection stage; flexible working arrangements for Peer Workers can have the unintended effect of perpetuating hierarchies within teams; the maintenance of protective practice boundaries through supervision and training can militate against the emergence of a distinctive body of peer practice; lack of consensus around what constitutes peer practice can result in feelings for Peer Workers of inequality, disempowerment, uncertainty about identity and of being under-supported.ConclusionsThis research is indicative of potential benefits for mental health service teams of introducing Peer Worker roles. Analysis also suggests that if the emergence of a distinctive body of peer practice is not adequately considered and supported, as integral to the development of new Peer Worker roles, there is a risk that the potential impact of any emerging role will be constrained and diluted.