Article 166 of the Constitution requires the courts to issue reasoned and documented decisions based on the laws and principles underlying the verdict. The importance of interpretative principles in labor law is widely recognized due to its protective nature. In cases of ambiguity, vagueness, or lack of legal texts, the aforementioned protective principles for the weaker party (the worker) are upheld. The current research was conducted using a descriptive-analytical method, supported by the library data and judicial opinions, to identify the substantive principles in labor law that protect workers. Initially, it was assumed that various principles could be identified within legislative texts, judicial opinions and legal doctrine. However, this research revealed that, firstly, many principles of worker protection, despite their implicit existence, have not been recognized; and secondly, in addition to the known principles mentioned above, other principles such as the broad interpretation in favor of the worker, the principle of limiting the will of the worker, the principle of minimum benefits in labor law, the principle of maximum obligations in labor law, the principle of prioritizing workers’ rights, the principle of valuing workers’ labor, and  the principle of continuity of the workplace were raised and examined.