Purpose: The purpose of this paper is to present the transdisciplinary case study (TCS) as a learning framework based on what we call functional socio-cultural constructivism and project-based learning (PBL). In doing so, the paper attempts to illustrate the applicability of TCS to learn competencies and skills necessary to research problems of sustainable development. Design/methodology/approach: TCS is considered a learning framework based on the principle of self-regulated learning; i.e. students must actively deal with the requirements as well as plan and execute their project work within their own worldviews and goals. TCS methods are essential as we tackle complex real-world problems. Findings: The paper discusses challenges and obstacles of such an approach and present lessons learned since 1994, on both the viewpoints of students and of teachers. It conclude that case study learning is a demanding task, especially in a transdisciplinary context where more challenges emerge than in PBL, since goals of teachers, case agents, and students have to be balanced. Practical implications: TCS or courses like it are important for universities at the present time. Under present budget restrictions and a wide-ranging mistrust of society toward universities, there is a necessity for a new contract between society and research: students should learn to take over responsibility in societal contexts and be able to communicate beyond the "ivory tower." Originality/value: The learning goals of TCS differ from the goals of most university courses. They are more comprehensive and include complex problem solving, societal context, and group processes. The ambitious goal is that students become enabled to tackle complex, real-world problems. (Contains 5 figures, 1 table, and 2 notes.)