Co-production is commonly conceptualised as a more equal sharing of power and decision-making between a dichotomy of service user and service provider, each bringing valuable and different assets to the process. ‘Experts by experience’ lie in the overlap between this conceptually created duality, providing the services they now do by virtue of having once used services themselves. Previous related studies suggest that their involvement in co-production could impact positively on their social capital, self-esteem, self-efficacy and life skills. However, no studies have been explicitly psychological or phenomenological in nature, and the theoretical basis for such outcomes remains under-developed. This phenomenological study explored the psychological impact of co-production for young people who were paid ‘experts by experience’ for a young person's mental health charity in a large and diverse urban area in the UK, looking at the ‘what’ of psychological impact, as well as the theoretical ‘why?’ and ‘how?’. Semi-structured interviews were conducted with a convenience sample of five males, with a mean age of 25 years. Interpretative phenomenological analysis yielded three master themes: ‘the co-production approach’, ‘I'm a professional’ and ‘identities in transition’. Participants valued a collegiate organisational approach that prioritised empowerment, agency and equality between ‘experts by experience’ and ‘experts by qualification’, leading to a positive impact on their self-efficacy and self-esteem. Co-production impacted fundamentally on their identity structure, enabling them to explore a new identity as a ‘professional’. The results are framed within identity process theory and point to the potential benefits of this model to co-production.