BACKGROUND: HCV disproportionately affects marginalized communities such as homeless populations and people who inject drugs (PWID), posing a challenge to traditional health services. The HepFriend initiative in London is a model of care utilizing HCV outreach screening and peer support to link vulnerable individuals to HCV treatment in secondary care. OBJECTIVES: To assess the cost-effectiveness of the HepFriend initiative from a healthcare provider perspective, compared with standard-of-care pathways (consisting of testing in primary care and other static locations, including drug treatment centres, and linkage to secondary care). METHODS: Cost-effectiveness analysis using a dynamic HCV transmission and disease progression model among PWID and those who have ceased injecting, including housing status and drug treatment service contact. The model was parameterized using London-specific surveillance and survey data, and primary intervention cost and effectiveness data (September 2015 to June 2018). Out of 461 individuals screened, 197 were identified as HCV RNA positive, 180 attended secondary care and 89 have commenced treatment to date. The incremental cost-effectiveness ratio (ICER) was determined using a 50 year time horizon. RESULTS: For a willingness-to-pay threshold of £20000 per QALY gained, the HepFriend initiative is cost-effective, with a mean ICER of £9408/QALY, and would become cost saving at 27% (£10525 per treatment) of the current drug list price. Results are robust to variations in intervention costs and model assumptions, and if treatment rates are doubled the intervention becomes more cost-effective (£8853/QALY). CONCLUSIONS: New models of care that undertake active case-finding with enhanced peer support to improve testing and treatment uptake amongst marginalized and vulnerable groups could be highly cost-effective and possibly cost saving.