Unionization may have important implications for the delivery of nursing home care, but little is known about this phenomenon. Since 1985, the proportion of nursing home workers covered by union contracts declined from 14.6% to 9.9%. The first national-scale data on facility-level unionization reveals that unions are more common in nursing homes with more residents, in hospital-based or chain-affiliated facilities, and in facilities serving a higher proportion of Medicaid patients. With new federal policy proposals aimed at substantially lowering the cost of organizing workers, policymakers will want to consider the potential impact of nursing home unionization on worker, patient, and market outcomes.