The rate of HCV infection is higher in people with psychiatric conditions than in the general population. However, access to somatic care for populations with mental or dual diagnoses remains insufficient. These circumstances could constitute a barrier to the eradication of HCV infection. A retrospective study was performed in the public mental health institution of Ville Evrard. Screening for HCV infection should be systematically proposed to patients attending the institution. On-site assessment of liver disease severity and treatment with direct-acting antivirals prescribed by physicians not specialised in hepatology allowed a better continuum of care. Patients lost to follow-up after a positive HCV serology test without viral load assessment were contacted. Patients hospitalised at least once a year were included. 8520 patients out of 18,439 (46.2%) were screened for HCV infection between 2017 and 2021. The screening rate increased from 40.0% in 2017 to 65.7% in 2021. HCV seroprevalence was 2.2%. A total of 129 HCV PCRs were performed, and 27.1% were positive. In a logistic regression model, patients older than 30 years were at greater risk of having a positive HCV serology test. These positive serologies were 1.9 times higher in men than women (p < 0.001). The assessment of fibrosis was found in 45.7% of patients with a positive HCV PCR. Patients with psychiatric conditions constitute an important HCV reservoir. A strategy of screening and management of HCV infection in this population appears to be feasible. This strategy could contribute to the eradication of chronic HCV infection.