ABSTRACT The prevalence of outdoor sports tourism has posed certain threats to the natural environment. In recent years, incidents of outdoor sports enthusiasts damaging ecological environments and historical sites have become increasingly common. Thus, it is imperative to encourage these enthusiasts to protect environmental ecosystems, and sustainability has become a priority consideration for those participating in outdoor sports tourism. This paper explores the multiple mediating roles of environmental knowledge and attitudes in the relationship between sustainable values and the pro-environmental behaviours of outdoor sports tourism enthusiasts. The study aims to provide references and suggestions for promoting environmentally responsible behaviours in outdoor sports tourism and to support the sustainable development of sports tourism in China and globally. The research targets outdoor sports tourism enthusiasts, analysing data from 1079 survey responses. Structural Equation Modeling (SEM) is used to test the direct and indirect effects between variables. The results indicate that sustainable values have a positive impact on environmental attitudes, environmental knowledge, and pro-environmental behaviours. Furthermore, environmental attitudes and knowledge play a positive mediating role between sustainable values and pro-environmental behaviours. Lastly, this paper offers substantial suggestions to promote the sustainable development of outdoor sports tourism.