Background <p>Sustainability has become an important consideration in the twenty-first century, with physical education contributing to students' cognitive, affective, and psychomotor development. Physical education teachers can promote sustainable lifestyles through their teaching practices. This study examines the relationship between intrapersonal and interpersonal mindfulness and sustainability competencies (social, economic, and environmental dimensions), along with the moderating role of demographic variables.</p> Methods <p>Data were collected from 852 physical education teachers in Turkey. Structural equation modeling and moderator analysis were used to analyze the relationships between mindfulness and sustainability competencies, and the moderating effects of gender, education level, and school level.</p> Results <p>Intrapersonal mindfulness showed a stronger association with sustainability competencies than interpersonal mindfulness. Demographic variables moderated this relationship, with female teachers, high school teachers, and those with postgraduate education exhibiting stronger links between mindfulness and sustainability competencies.</p> Conclusions <p>The findings suggest that mindfulness can support teachers in promoting sustainability. Professional development programs should consider integrating mindfulness training. Further research is needed to explore the relationship between mindfulness and sustainability in education and its implications for the Sustainable Development Goals.</p>