Police unions are widely recognized as having a major influence on American policing, with respect to day‐to‐day management, disciplinary procedures, and police–community relations. Despite this important influence, however, police scholars have neglected police unions. The reasons for this neglect are not clear, as scholars have investigated other highly sensitive police issues such as the use of excessive force and corruption. This paper examines the most important dimensions of the impact of unions on policing and outlines an agenda for future research.