Psychiatric patients are at high risk for contracting COVID-19, and inpatient psychiatric units face substantial risks of institutional outbreaks. Here, the authors describe an algorithm for testing and triage in a large psychiatric facility designed to prevent local COVID-19 transmission. The algorithm is based on expert opinion and clinical experience between March and April of 2020, during which the institution cared for 47 COVID-19 positive psychiatric inpatients. The implementation of the algorithm is designed to mitigate COVID-19 transmission, preserve the safest and least restrictive treatment environment for psychiatric inpatients, and provide a model adaptable to other institutional settings.