The association between social networks and improved mental and physical health is well documented in the literature, but mental health services rarely routinely intervene to improve an individual's social network. This review summarises social participation intervention models to illustrate different approaches which practitioners use, highlight gaps in the evidence base and suggest future directions for research. A systematic search of electronic databases was conducted, and social participation interventions were grouped into six categories using a modified narrative synthesis approach. Nineteen interventions from 14 countries were identified, six of which were evaluated using a randomised controlled trial. They were grouped together as: individual social skills training; group skills training; supported community engagement; group-based community activities; employment interventions; and peer support interventions. Social network gains appear strongest for supported community engagement interventions, but overall, evidence was limited. The small number of heterogeneous studies included in this review, which were not quality appraised, tentatively suggests that social participation interventions may increase individuals' social networks. Future research needs to use experimental designs with sufficient samples and follow-up periods longer than 12 months to enable us to make firm recommendations for mental health policy or practice.