The purpose of this study was to identify the factors influencing the sustainable development of sports tourism destinations in Garmsar County. The present research is an applied study conducted using a qualitative approach and the thematic analysis method. The statistical population included professors of sports management and tourism, heads of sports federations, and researchers in the fields of sports management and tourism. The research sample was selected from among the population members using purposive and snowball sampling methods. The research tool was semi-structured interviews conducted with 17 experts, which continued until theoretical saturation was reached. The validity of the research was confirmed by relevant experts, and the reliability was calculated to be 87% using the intra-subject agreement method. The results of the study indicated that the sustainable development of sports tourism destinations in Garmsar County consists of 78 initial codes, 12 central concepts, and 5 main categories. These categories include requirements for sustainable tourism development, access management, human resource management, institutional factors, and technological and innovative factors. Achieving sustainable development requires a shift from a project-oriented and short-term perspective toward a strategic and future-oriented vision. Sustainable development depends on continuity, institutional learning, and the active participation of all stakeholders—from local managers and investors to citizens and professionals in sports and tourism. Once this structural and institutional coordination is established, Garmsar County can become a successful model for sustainable sports tourism development in the country.