Purpose: The integration of ESD is a complex problem. It calls for an innovative, student-centred curriculum, as well as professional learning and agency, by which university teachers feel empowered to change their practice and direct their peers and institutions towards ESD. This study aims to explore what university teachers consider to be the most important attitudes in supporting their agency to deliver Education for Sustainable Development (ESD) via a Problem Based Learning (PBL) programme. Design/methodology/approach: This study presents a theoretical framework for professional agency comprising three domains--intrapersonal, action and environmental. A Q methodology is adopted to explore university teachers' perceptions of the most important environmental factors in supporting their ability to deliver ESD via a problem-based learning (PBL) programme. Twenty-eight participants from six Southeast Asian universities took part in a PBL-based professional development programme designed to improve teachers' ESD- and PBL-based skills and competencies. Findings: The results indicate that the participants were confident in their ability to implement PBL and saw PBL as an approach suitable for addressing current educational, professional and societal challenges. This study offers a series of recommendations to help university teachers develop their ESD and PBL practices. Originality/value: Although the literature on human agency is extensive, research surrounding teachers' professional agency in the context of ESD and PBL in higher education is lacking. The present study addresses this gap by capturing individual teachers' beliefs, perceptions and views and by using Q methodology to examine the subjectivity of study participants.