This study complements the discussion on theoretically derived competence models through an empirical analysis that gives a voice to teachers who are experienced in education for sustainable development (ESD). It adds their insights and expertise to the academic discourse. Our original contributions are threefold: (1) We find justification for aspects of pedagogical content knowledge (PCK) and content knowledge (CK), which share a common understanding of the relevance of competencies in teaching, and for the importance of acting on an institutional level. (2) We illustrate these competencies via an example from ESD in Germany. (3) We contribute to the discussion of ESD by adding (a) the view of the teachers, (b) the drivers behind and barriers to ESD as reported by the investigated teachers themselves, and (c) an ascertainment of the structural competencies of ESD teachers in terms of their awareness of structures and hierarchies and the communication patterns used therein. We interviewed 12 teachers involved in ESD at German elementary schools and identified two types of ESD teachers. Both types aim to contribute to social change through their ESD activities; however, the teachers display different sets of competencies when it comes to integrating ESD into teaching.