This chapter addresses the limited exploration of design-based learning (DBL) in the context of sustainability education within the built environment. While there has been a growing body of work on DBL in STEM and architecture, there has been limited comprehensive studies examining its impact on developing sustainability leaders. This study seeks to fill this gap by providing a detailed case study of how a multi-university design competition, rooted in DBL principles, can effectively cultivate the skills and competencies needed for leadership in sustainable built environment practices. The findings demonstrate how integrating real-world challenges and industry engagement into DBL through design competitions not only enhances students’ technical and soft skills but also provides valuable insights into industry practices, thereby better preparing students for their future careers. Additionally, the study highlights the importance of interdisciplinary collaboration and cross-cultural engagement in addressing the complex challenges of sustainability, suggesting that these elements are crucial for the effective application of DBL and design competitions in higher education. This chapter contributes to the broader discourse on DBL by extending its application to sustainability education and offering a model for enhancing the preparation of future sustainability leaders through design competitions.