Gamification is a new trend that has gained increasing importance in climate protection. In recent years, researchers have begun to integrate game elements into non-gaming contexts to encourage green behaviors. The city of Sierre jumped on the bandwagon and initiated a project aiming to use gamification to encourage its population to engage in green behaviors. The research focuses on identifying the barriers and motivators for people to engage in green actions in order to diminish or enhance them using games. Followed by a series of focus groups, 10 in-depth semi-structured interviews were conducted. The main result shows a significant gap between attitude and behavior despite a high level of awareness and positive sustainable intentions. Based on research propositions that have been confronted with the scientific literature, Sierre has therefore collaborated with the HES-SO Valais-Wallis to realize a gaming app on the theme of sustainable development for the population called ECOTREE.