Teachers face a variety of challenges and stressors that can erode their well-being over a long period. Compassion and mindfulness are known to affect teachers' social-emotional competence. Psychological flexibility means that individuals accept things beyond their control and are determined to continue the actions that can make their lives meaningful. This study aims to investigate the mediating role of psychological flexibility in the relationship between teachers' mindfulness and fears of compassion. This research is based on a cross-sectional survey design. The study sample consists of 251 teachers. The instruments used include the Fears of Compassion Scale, the Mindfulness in Teaching Scale, the Acceptance and Action Questionnaire II, and a researcher-developed personal information form. Findings indicate that psychological flexibility plays a partial mediating role in the relationship between mindfulness in teaching and fears of compassion. Based on the research findings, it can be argued that mindfulness in teaching, psychological flexibility, and fears of compassion are important in the classroom for both teachers and students. The foundational elements of psychological flexibility (e.g., being present at the moment, acceptance, diffusion, contextual self, values, and the ability to act in line with these values) can contribute to nurturing teachers' mindfulness skills in teaching. This, in turn, facilitates teachers in creating a compassionate, democratic, and supportive classroom atmosphere for students.