Law No. 6325 on Mediation in Civil Disputes introduced mediation as one of the alternative dispute resolution methods, and Law No. 7036 on Labour Courts stipulates mediation as a way to be applied before filing a lawsuit in disputes between the employee and the employer. In lawsuits filed for employee or employer receivables and compensation based on the law, individual or collective labour agreement and for reinstatement, the application to the mediator is regulated as a condition of litigation. After the mediation activity, if an agreement is reached between the parties to the dispute, a mediation agreement document determining the scope of the agreement is issued. In cases where the subject matter of the mediation agreement document, which is a contract of the law of obligations in the sense of substantive law, is contrary to the mandatory rules, personal rights, morality, the will of the employee is impaired or overused, it is necessary to go beyond the rule that no lawsuit will be filed on the matters agreed in mediation and its invalidity must be demonstrated by the judgement. In the face of the power imbalance between the employee and the employer in labour disputes, the supervision of the validity of the agree-ment documents by the courts may prevent the manipulation of the employee by the employer and the deepening of the power imbalance between the parties during the mediation process.