The State Board of Mediation is a quasi-judicial board that administers the Public Sector Labor Law (RSMo. Chapter 105.500 - 105.598), which covers most public sector employees who seek union representation.

The board defines an appropriate bargaining unit of employees based on whether or not they share a community of interest and, if certified, determines majority representation status by conducting a secret ballot election. Jurisdiction includes all counties, cities, school districts, special districts, and departments of state government, with a few exceptions.