The aim of the present study was to explore the lived experiences and perceptions of physical education teachers in order to identify factors affecting their participation in school sports in Tehran. This study was qualitative and was conducted with a phenomenological approach. Participants included physical education teachers in Tehran schools who were selected through purposive sampling (N=19). Data were collected through semi-structured interviews and analyzed using thematic analysis. The results of the study showed that several factors affect the participation of physical education teachers in school sports, which can be categorized into several main axes. These factors included individual factors (motivation, expertise, attitude), organizational factors (management, support, facilities, curriculum), and sociocultural factors (organizational culture, parental and community expectations). Finally, the findings of this study confirm that improving the quality of physical education requires a shift from a one-dimensional perspective to a systemic and comprehensive approach in which the removal of structural-economic barriers is pursued in parallel with the comprehensive empowerment of teachers as the main pillar and the active participation of all stakeholders (parents, administrators, and social institutions) in order to create a sustainable sports ecosystem. Based on the findings of this study, suggestions are provided for improving the participation of physical education teachers in school sports that can help policymakers and educational planners to improve the quality of physical education lessons and increase students' physical activity.