The proactivity in the management of sport events is essential to maximise environmental benefits for the host communities through strategic leverage. Therefore, this study aimed to understand the process of strategic environmental leverage in an international nature-based non-mega event of sport tourism (Sintra PRO 2022 - stage of the IBC World Bodyboarding Tour) by means of action research. Data collection combined several methods and sources, namely, document research, nominal group sessions, field observation, and interviews conducted with organisers and partners of the event. Three actions, which synergistically linked the environmental values of community projects and the sport subculture, were implemented in order to focus stakeholders' attention on the environmental topics. The availability of local resources and the involvement of the network of local partners facilitated the implementation of environmental leverage. On the other hand, the lack of communication between those involved in the operationalisation and promotion of environmental leverage actions was a constraint in the process. This study highlights several implications for environmental leverage in sport events, as well as for the applicability of the environmental leverage model to promote strategic planning and the implementation of the resulting strategic environmental leverage actions in sport events.