Despite the importance of school sports events in promoting students’ physical, psychological, and social well-being, their participation is influenced by multiple factors that should be identified for effective planning and policymaking. This study aimed to answer the following research question: What factors influence students’ participation in school sports events, and how can these factors be classified? This applied study adopted a qualitative approach based on thematic analysis. The study population consisted of students, teachers, and parents from Iranian schools. Sixteen participants with experience in school sports events were selected through purposive sampling. Data were collected through semi-structured interviews until theoretical saturation was reached and analyzed using open and axial coding. The findings revealed that the factors influencing students’ participation could be classified into four main domains: psychological and individual, cultural and social, economic, and infrastructural and environmental factors. Motivation, physical competence, academic status, and psychological pressures were identified as the main psychological factors. Family support, the roles of teachers and school principals, school culture, and the quality of social interactions were the key cultural and social factors. Economic constraints, the costs of sports activities, access to sports facilities, the quality of equipment, and the safety of sports environments also significantly influenced students’ participation. The findings indicate that increasing students’ participation in school sports events requires a comprehensive approach addressing individual, social, economic, and infrastructural factors simultaneously. These findings can provide a basis for policymaking and planning to promote students’ participation in school sports events