This study investigated the effectiveness of a negotiation simulation role-playing game as a pedagogical tool for developing the sustainability competences of university engineering students. In an active learning environment, students engaged in a roleplaying exercise, assuming the roles of diverse stakeholders debating the future of a coal-burning plant in the fictional city of Pinehill. The research examined how an experiential, yet safe real-world simulation influenced the development of key sustainability competences, such as systems thinking, strategic collaboration, and future-oriented analytical thinking, which are essential skills for navigating complex sustainability transitions. With perspectives of different actors 'embodied' during the simulation, the game also enhanced the ability to consider diverse viewpoints in decision-making. Data was collected through group reflection reports and surveys, utilizing both qualitative and quantitative methods to assess students' learning experiences and competence development. It was observed that participation in the simulations empowered students with deepened competences in sustainability, especially regarding interpersonal skills. This research contributes to engineering education by presenting that simulation roleplaying games can narrow the gap between theoretical knowledge and real-world application while developing key sustainability competences that traditional classroom methods are unlikely to deliver.