Background Although people who inject drugs (PWID) are an important group to receive Hepatitis C Virus (HCV) antiviral therapy, initiation onto treatment remains low. Concerns over reinfection may make clinicians reluctant to treat this group. We examined the risk of HCV reinfection among a cohort of PWID (encompassing all those reporting a history of injecting drug use) from Scotland who achieved a sustained virological response (SVR). Methods Clinical and laboratory data were used to monitor RNA testing among PWID who attained SVR following therapy between 2000 and 2009. Data were linked to morbidity and mortality records. Follow-up began one year after completion of therapy, ending on 31st December, 2012. Frequency of RNA testing during follow-up was calculated and the incidence of HCV reinfection estimated. Cox proportional hazards regression was used to examine factors associated with HCV reinfection. Results Among 448 PWID with a SVR, 277 (61.8%) were tested during follow-up, median 4.5 years; 191 (69%) received one RNA test and 86 (31%) received at least two RNA tests. There were seven reinfections over 410 person years generating a reinfection rate of 1.7/100 py (95% CI 0.7–3.5). For PWID who have been hospitalised for an opiate or injection related cause post SVR (11%), the risk of HCV reinfection was greater [AHR = 12.9, 95% CI 2.2–76.0, p = 0.002] and the reinfection rate was 5.7/100 py (95% CI 1.8–13.3). Conclusion PWID who have been tested, following SVR, for HCV in Scotland appear to be at a low risk of reinfection. Follow-up and monitoring of this population are warranted as treatment is offered more widely.