Abstract Background Despite growing interest in workplace mental health interventions, evidence of their effectiveness is mixed. Implementation science offers a valuable lens to investigate the factors influencing successful implementation. However, evidence synthesis is lacking, especially for small-to-medium-sized enterprises (SMEs) and for specific work sectors. The objectives of this review are to establish the scope of research with explicit analysis of implementation aspects of workplace mental health interventions and to identify barriers and facilitators to implementation in general and within SMEs and selected sectors. Methods A systematic scoping review and meta-synthesis of mixed methods process evaluation research from 11 databases, with the evaluation of methodological quality (MMAT) and confidence in findings (CERQual), was conducted. We selected information-rich studies and synthesised them using domains within the Nielsen and Randall implementation framework: context, intervention activities, implementation; and mental models. Results We included 43 studies published between 2009 and 2022, of which 22 were rated as information-rich to be analysed for barriers and facilitators. Most studies were conducted in healthcare. Facilitators reflecting ‘high confidence’ included: relevant and tailored content, continuous and pro-active leadership buy-in and support, internal or external change agents/champions, assistance from managers and peers, resources, and senior-level experience and awareness of mental health issues. Healthcare sector-specific facilitators included: easy accessibility with time provided, fostering relationships, clear communication, and perceptions of the intervention. Stigma and confidentiality issues were reported as barriers overall. Due to the small number of studies within SMEs reported findings did not reach ‘high confidence’. A lack of studies in construction and Information and Communication Technology meant separate analyses were not possible. Conclusions There is dependable evidence of key factors for the implementation of workplace mental health interventions which should be used to improve implementation. However, there is a lack of studies in SMEs and in a larger variety of sectors. Systematic review registration Research Registry ( reviewregistry897 ).

Barriers and facilitators to implementing workplace interventions to promote mental health: qualitative evidence synthesis