Hepatitis C virus (HCV) reinfection following successful treatment threatens the achievement of HCV elimination. The primary aim of this study is to assess reinfection rate three years after sustained virologic response (SVR) in people who inject drugs (PWID) that are on opioid agonist treatment (OAT) who underwent anti-HCV treatment with interferon-free regimens.Observational, non-interventional, prospective, descriptive study carried out in Spanish tertiary public hospitals between 2017 and 2022. Participants comprised 186 adult HCV infected individuals, 85.5% males with a mean age (Standard Deviation, SD) of 50.1 (5.9). All were enrolled in an OAT program at baseline and had attained SVR 12 weeks after therapy completion with an interferon-free treatment. Baseline data were abstracted from medical chart information collected through the routine clinical practice.The overall rate of HCV reinfection three years after SVR12 among PWID was 1.2 new cases per 100 person-years of follow-up at a median of 15.9 months. In the subgroup analyses, those with injection drug practice and without a stable housing had higher reinfection rates.Although PWID in OAT present a low rate of reinfection by HCV after successful treatment, a closer monitoring in the first year and strengthening inter-consultations with services responsible for monitoring addiction in these patients will be crucial to reduce risky behaviors avoiding HCV reinfection.