ObjectivesTo establish the evidence base for the effects on health outcomes and costs of social prescribing link workers (non-health or social care professionals who connect people to community resources) for people in community settings focusing on people experiencing multimorbidity and social deprivation.DesignSystematic review and narrative synthesis using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.Data sourcesCochrane Database, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, EU Clinical Trials Register, CINAHL, Embase, Global Health, PubMed/MEDLINE, PsycInfo, LILACS, Web of Science and grey literature were searched up to 31 July 2021. A forward citation search was completed on 9 June 2022.Eligibility criteriaControlled trials meeting the Cochrane Effectiveness of Practice and Organisation of Care (EPOC) guidance on eligible study designs assessing the effect of social prescribing link workers for adults in community settings on any outcomes. No language restrictions were applied.Data extraction and synthesisTwo independent reviewers extracted data, evaluated study quality using the Cochrane EPOC risk of bias tool and judged certainty of the evidence. Results were synthesised narratively.ResultsEight studies (n=6500 participants), with five randomised controlled trials at low risk of bias and three controlled before–after studies at high risk of bias, were included. Four included participants experiencing multimorbidity and social deprivation. Four (n=2186) reported no impact on health-related quality of life (HRQoL). Four (n=1924) reported mental health outcomes with three reporting no impact. Two US studies found improved ratings of high-quality care and reduced hospitalisations for people with multimorbidity experiencing deprivation. No cost-effectiveness analyses were identified. The certainty of the evidence was low or very low.ConclusionsThere is an absence of evidence for social prescribing link workers. Policymakers should note this and support evaluation of current programmes before mainstreaming.PROSPERO registration numberCRD42019134737.