Objectives. To evaluate a daily antigen testing program for health care personnel. Methods. We examined antigen testing results between December 13, 2020, and April 30, 2021, from 5 forensic psychiatric inpatient hospitals throughout California. Results. Among 471 023 antigen tests administered, 449 positives (0.0036% false positives) were detected. Conclusions. Antigen tests had low false-positive rates, high positive predictive value, and high levels of acceptability, important characteristics when considering their application in the community. Public Health Implications. Daily antigen testing was feasible and should be considered to reduce COVID-19 transmission. (Am J Public Health. 2022;112(3):467-471. https://doi.org/10.2105/AJPH.2021.306588).