Due to global trends in rising resource consumption and environmental degradation, numerous professional organizations like the National Academy of Engineering and the National Society of Professional Engineers have called on the engineering profession to address sustainable development in their projects and decision-making. For engineers to effectively contribute to global sustainable development, they must learn to understand and apply sustainability concepts in problem-solving and design. Typically in design classes, undergraduate students have difficulty integrating or building on knowledge from other engineering and non-engineering courses to evaluate the broader context for their decision-making. Therefore, the goal of this project is to develop and assess a sustainable design framework for instruction in upper-level design courses that develops students' ability to apply complex knowledge across different problem contexts. As potentially cross-cutting features of engineering curricula, "design" and "sustainability" represent an opportunity for integration and development of a unifying thread for engineering problem-solving.<br/><br/>The proposed research uses a novel application of cognitive flexibility theory to the complex and ill-structured domain of sustainable engineering design, intended to prepare students for solving societal challenges of sustainable development. The project team seeks a better understanding of how students learn and how they use and transfer knowledge of sustainable design thinking, tools, and processes in new settings. Of particular importance is how these experiences help to make better engineers and could lead to better outcomes for all career destinations. The team will employ a mixed-methods approach to measure the depth and breadth of such learning. Guided by four research questions, it is anticipated that: (a) classification of real-world sustainable design problems will lead to an understanding and characterizing of complex problem solving domains and processes, (b) students' learning outcomes (cognitive, affective, social, and professional) will be assessed in order to understand how these problems enable cognitive abilities, (c) innovative instruments and assessment tools, that can be transferred across institutions, programs, departments, and experiences, will be developed, and (d) strategies for implementing complex sustainable design problem solving in engineering education will be investigated. Through this project a broad community of practice of engineering educators will be established across disciplines, as design instruction is incorporated into all accredited engineering programs and as the challenge of sustainable development is a call to all engineers.