More than 40 percent of all reported coronavirus disease 2019 (COVID-19) deaths in the United States have occurred in nursing homes. As a result, health care workers' access to personal protective equipment (PPE) and infection control policies in nursing homes have received increased attention. However, it is not known whether the presence of health care worker unions in nursing homes is associated with COVID-19 mortality rates. Therefore, we used cross-sectional regression analysis to examine the association between the presence of health care worker unions and COVID-19 mortality rates in 355 nursing homes in New York State. Health care worker unions were associated with a 1.29-percentage-point reduction in mortality, which represents a 30 percent relative decrease in the COVID-19 mortality rate compared with facilities without these unions. Unions were also associated with greater access to PPE, one mechanism that may link unions to lower COVID-19 mortality rates.