The primary aim of this study was to evaluate the impact of drug consumption rooms (DCRs) in France on injection equipment-sharing, while the secondary aims focused upon their impact on access to hepatitis C virus (HCV) testing and opioid agonist treatment (OAT). The COhort to identify Structural and INdividual factors associated with drug USe (COSINUS cohort) was a 12-month longitudinal study of 665 people who inject drugs (PWID), conducted in Bordeaux, Marseille, Paris and Strasbourg. We used data from face-to-face interviews at enrolment and at 6-month and 12-month visits. The participants were recruited in harm reduction programmes in Bordeaux and Marseille and in DCRs in Strasbourg and Paris. Participants were aged more than 18 years, French-speaking and had injected substances the month before enrolment. We measured the impact of DCR exposure on injection equipment sharing, HCV testing and the use of medications for opioid use disorder, after adjustment for significant correlates. We used a two-step Heckman mixed-effects probit model, which allowed us to take into account the correlation of repeated measures and to control for potential bias due to non-randomization between the two groups (DCR-exposed versus DCR-unexposed participants). The difference of declared injection equipment sharing between PWID exposed to DCRs versus non-exposed was 10% (1% for those exposed versus 11% for those non-exposed, marginal effect = -0.10; 95% confidence interval = -0.18, -0.03); there was no impact of DCRs on HCV testing and OAT. In the French context, drug consumption rooms appear to have a positive impact on at-risk practices for infectious diseases such as human immunodeficiency virus (HIV) and hepatitis C virus.< Réduire