BACKGROUND AND AIMS: Previous studies have shown low rates of diagnosis and treatment of hepatitis C virus (HCV) infection in people who inject drugs (PWID). Our aims were to test the effect of a complex intervention [Hepatitis C Awareness Through to Treatment (HepCATT)] in drug and alcohol clinics-primarily, on engagement of HCV-positive PWID with therapy and, secondarily, on testing for HCV, referral to hepatology services and start of HCV treatment. DESIGN AND SETTING: A non-randomized pilot study in three specialist addiction clinics in England comparing an intervention year (starting between September 2015 and February 2016) with a baseline year (2014), together with three control clinics. PARTICIPANTS: Analysis included all attendees at the intervention and control specialist addiction clinics identified as PWID. INTERVENTION: The intervention comprised the placement of a half-time facilitator in each clinic for 12 months with the brief to increase diagnosis of HCV infection within clients at those services and the engagement of diagnosed individuals with an appropriate care pathway. The facilitator undertook various activities, which could include training of key workers, direct interaction with clients, streamlining and support for hepatology appointments and introduction of dried blood-spot testing. MEASUREMENTS: For each clinic and period, we obtained the total number of clients and, as relevant, their status as PWID, tested for HCV, known HCV-positive, engaged with HCV therapy or treated. FINDINGS: Compared with baseline, there was strong evidence that engagement with HCV therapy in the intervention year increased (P < 0.001) more in the HepCATT centres than controls, up + 31 percentage points [95% confidence interval (CI) = 19-43] versus -12 (CI = -31 to + 6) and odds ratio (OR) = 9.99 (CI = 4.42-22.6) versus 0.35 (CI = 0.08-1.56). HepCATT centres also had greater increases in HCV testing (OR = 3.06 versus 0.78, P < 0.001), referral to hepatology (OR = 9.60 versus 0.56, P < 0.001) and treatment initiation (OR = 9.5 versus 0.74, P < 0.001). CONCLUSIONS: Introducing a half-time facilitator into drug and alcohol clinics in England increased engagement of HCV-positive people who inject drugs with hepatitis C virus care pathways, with increased uptake also of testing, referral to hepatology and initiation of treatment.