Psychological theory and research can make key contributions to sustainability scholarship and practice, as is demonstrated here in the field of higher education pedagogy. College students undergo profound changes in epistemological assumptions and in identity during their undergraduate years. Data on the Measure of Intellectual Development for students participating in learner-centred pedagogies at Western Washington University in Bellingham, Washington, showed a trend toward more complex thinking by these students (N=153). Qualitative data on student identity development associated with transdisciplinary, project-based campus sustainability courses were collected at Canada’s University of Prince Edward Island and at Western Washington University in Bellingham. Findings revealed the identity of “learner” blending with that of “change agent”; a greater sense of identity in relation to the campus community and the different perspectives of its stakeholders, the sustainability movement; and a sense of empowerment backed up by practical skills. Sustainability poses new challenges for intellectual-moral development and identity development. Psychological theory gives insights into how pedagogies should be designed to challenge students just beyond their level of intellectual, moral, and identity development, in order to expose them to intellectual-moral growth and identity alternatives conducive to the complexities of sustainability advocacy and practice.