A theory behind, and the practicalities of the notion of fairness in labour law are examined. An effort is made to justificate the existence of the principle of fairness in labour law. The rules of labour legisation as well as the judical practice reflecting the concept of fairness are analyzed. The criteria of measurement of fairness of participants of labour law relations are designated. The pathways to troubleshoot the deficienties of legislation and prevention of abuse of right are proposed. Considering the lack of accurate criteria of abuse of right, the notion of fair practice have to be invoked continuously when the fundamentals of legislation are invoked. Accounted the limited capability of use of the entity of fairness in labour sphere. Regarding relations that bear the "private-public" characteristic, the preference is to be devolved to protection of rights and interests of the worker. The existence of the principle of fairness in labour law is justified, along with the necessity to secure it in legislation.