According to Article 18 of the Labor Law No. 4857, the employer who wishes to terminate the employment contract of an employee cove- red by job security with a notice of termination, has to rely on a valid reason arising from the competence or behavior of the worker or the requirements of the business, workplace or job. Subparagraph II of Ar- ticle 25 of the Labor Law also regulates the justified reasons that allow the termination of the employment contract with just cause without noti- ce. In practice, it is frequently encountered that the social media posts of the worker are shown as valid or justified reasons for the termination of the employment contract. In our study, it is focused on whether the ter- mination of the employment contract by the employer of the employee's social media posts within the scope of employee behavior can be consi- dered as a valid or justified reason, and the current situation is evalua- ted in line with the Supreme Court decisions.