To bring about the rapid transformative change needed to address the global sustainability crises, a paradigm shift is needed, characterized by more sustainable beliefs and attitudes. Therefore, this thesis explores the potentials of an escape game intervention as a new strategy to promote sustainable attitudes and beliefs in players, focusing on environmental sustainability. Firstly, a framework was created with Five Pillars for a successful environmental escape game: Fun, Experiential, Urgent, Problem-Rewarding and Social. Afterwards, this Five Pillars Framework guided the design and evaluation of an Environmental escape game called “Unlock the Future”. Based on the framework, an escape game with the Five Pillars was expected to increase players’ environmental attitudes and efficacy beliefs. To test this assumption, pre- and post-survey data was gathered from nine teams who played the escape game, using validated scales for environmental attitude, self-efficacy and collective efficacy, as well as an adapted version of the Game User Experience Satisfaction Scale. The survey results confirmed that all Five Pillars were present in the escape game design, and as a result players’ environmental self-efficacy and collective efficacy increased after playing the game. However, this effect was not present for players’ environmental attitude, nor for participants that were game hosts, or failed at the escape game.