The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has severely affected health care workers (HCWs).¹ As a result, hospital systems began testing HCWs² and implementing infection control measures to mitigate workforce depletion and prevent disease spread.³ Mass General Brigham (MGB) is the largest health care system in Massachusetts, with 12 hospitals and more than 75 000 employees. In March 2020, MGB implemented a multipronged infection reduction strategy involving systematic testing of symptomatic HCWs and universal masking of all HCWs and patients with surgical masks.⁴ This study assessed the association of hospital masking policies with the SARS-CoV-2 infection rate among HCWs.