 This systematic review examines the evidence and experience of service user and caregiver involvement in mental health systems strengthening in low and middle income countries, as well as models of best practice for evaluation of capacity-building activities that facilitate their greater participation. The review found a lack of high-quality research and a weak evidence base for the work being conducted across countries, with most service user involvement having taken place within advocacy and service delivery. Further research on this topic is recommended, particularly research that includes more rigorous evaluation. This article was authored by Maya Semrao, Heidi Lemp, Roxanne Kingjad, and others.