Discipline is the condition of a community that meticulously and diligently abides by its laws and its written or unwritten rules regarding the order. Discipline is necessary for trade union organizations to achieve their goals, as in any organization. Organization means trade unions and confederations. The Disciplinary Board is listed among the mandatory bodies of the organizations in the Trade Unions and Collective Bargaining Code. Although there are no detailed articles about organs except the general assembly, common provisions regarding these organs are included under a separate article title. Therefore, it can be said that the duties and powers of the disciplinary board in trade unions are rather developed with practice and case law. In the study, firstly, general information about the disciplinary boards in trade unions in terms of Code No.6356 was given. In this section, the formation of disciplinary boards, membership, their duties, process and the mechanism of objection against their decisions are evaluated. In the second part, some Supreme Court decisions regarding trade union discipline practices are examined.