Across the United States, there is an increasing trend among medical residents to join unions. Even though these entities have existed for almost 100 years, escalating concerns regarding compensation, working conditions, and other factors have influenced thousands of residents to join unions. Unionization can both positively and negatively affect residents, hospital networks, and the communities that the system serves. Most resident unions are nationally organized, but the laws and rules governing these bodies vary among the 50 states. The individual states regulate the collective bargaining of the union with the health-care system, and physician leaders should be aware of the nuances regarding unions at their workplace setting.