PURPOSE: This study aimed to present the methods for screening, monitoring, and intervening with patients at high risk for mental health issues with COVID-19 at residential treatment centers, which are isolation treatment facilities for COVID-19 patients. METHODS: We evaluated the mental health status of COVID-19 patients in three residential treatment centers. At admission and one day before discharge, patients received via their mobile a questionnaire containing one question each on anxiety, subjective psychological distress, post-traumatic stress symptoms, depression and suicidal ideation to identify those at high risk for mental health issues. High-risk patients and normal-risk participants who requested consultation were referred for psychological counseling. We evaluated the participants' clinical and mental health characteristics and performed a logistic regression analysis to identify factors associated with worsened depression and suicide risk at discharge. RESULTS: Of 5,163 qualifying patients, 1,941 patients (37.6%) had their mental health assessed both at admission and discharge. In total, 661 persons (34.1%) required mental health support at admission and 648 persons (33.4%) at discharge. The patients at high risk for mental health issues at admission had an odds ratio of 5.31 (95% CI: 4.23-6.66) for depression at discharge, compared to those with normal mental health status at admission. The group that requested professional psychological counseling at admission showed an odds ratio of 2.33 (95% CI: 1.31-4.13) for depression at discharge. CONCLUSIONS: Repeated mental health monitoring is crucial for COVID-19 patients. Additionally, a flexible intervention strategy should be developed to implement different screening methods for patients at high risk for mental health issues, depending on the status of the COVID-19 epidemic and available resources.