© 2015 Elsevier B.V. Background: Among people who inject drugs (PWID), the prevalence of hepatitis C virus (HCV) infection is high; however HCV treatment uptake remains low. New models of care are needed to address the growing burden of HCV-related disease in PWID and to understand the barriers to assessment and treatment of HCV. This study evaluated assessment and treatment for HCV infection among PWID attending an opioid substitution treatment (OST) clinic with an integrated peer support worker model. Methods: Clients with a history of IDU and chronic HCV infection, attending the Newcastle Pharmacotherapy Service, Newcastle Australia, were recruited as part of a multisite prospective observational study (the ETHOS Cohort). Additional chart review was conducted for clients not enrolled in the ETHOS Cohort. A peer support worker was introduced to complement and extend services offered by the clinical team. Client contacts and assessments with a nurse and/or peer worker were evaluated, including those who commenced HCV treatment. Results: A total of 1447 clients attended the OST service during February 2009 and June 2014. Of these, 378 (26%) were assessed by a nurse and 242 (17%) by a clinician. HCV treatment was commenced by 20 (5%) participants and 15 (75%) achieved a sustained virological response (SVR). During May 2009 and July 2011, 332 nurse contacts and 726 peer worker contacts were evaluated. The nurse-led contacts were related to HCV treatment (50%) and review of pathology tests (34%), whereas peer worker contacts included discussion about HCV treatment (75%), education, counselling and/or support (53%) and general discussion about HCV infection (59%). Conclusion: These data demonstrate that peer support workers facilitate broader discussion about HCV treatment, education and/or support, allowing nurses to focus on HCV-related assessment and treatment. HCV treatment uptake was very low in this cohort, but SVR was high. The integration of peer support workers in treatment programs within OST clinics may address barriers to HCV care, but further studies are needed to assess their impact on assessment and treatment outcomes.