ABSTRACTPeer support specialists (PSSs) in mental healthcare services are individuals recovering from mental health conditions and providing formal peer support to clients with similar conditions. Despite evidence of the benefits of this modality and the increasing demand for it, little is known about the PSSs' experiences in mental healthcare services. This review systematically synthesises available qualitative data on the certified PSSs' experiences in providing formal peer support in mental healthcare services. A search was performed across six electronic databases and one grey literature database for all published and unpublished qualitative studies in English between 2014 and 2022. Mixed‐methods studies were included if their qualitative data were extractable. This review included PSSs who provided formal peer support to clients with similar mental health conditions. The included studies were appraised through the Critical Appraisal Skills Program Qualitative checklist, while data extraction was done through a customised tool. Our meta‐synthesis revealed an overarching theme on certified PSSs' journey in mental healthcare services, alongside four main themes: (i) emotional impacts of being PSSs, (ii) struggle to justify their roles, (iii) complex roles of PSSs and (iv) sources of support. The review has provided an insightful understanding of the PSSs' roles and needs, for which there is a need to cultivate a supportive working environment. Given the difficulties in adopting the PSSs' roles, as demonstrated by our findings, future research should explore how mental healthcare organisations can address their work‐related challenges and cultivate a supportive working environment.