This paper takes as its starting point the shift of emphasis in the field of environmental and sustainability education (ESE) towards the inclusion of social and human development issues. The paper deals with one of the basic guiding principles informing this transition and shift of focus, namely that of social justice framed in terms of our moral obligations to other humans in the Global South. The purpose of the paper is to explore how teachers integrate issues of social justice into their teaching on global sustainability. More specifically, this study investigates how a group of experienced teachers with an interest in global sustainability issues and experiences from North–South educational partnerships reflect on their own teaching. The chosen teachers had all been involved in development programmes and/or school cooperation projects with the aim to promote issues related to sustainable development which included North-South study visits for participating teachers and students. In the study I use postcolonial theory as a framework for the analysis in order to direct attention to and offer a deeper understanding of how historical processes, ethical relations to others, issues of power, and different forms of knowledge and knowing influence ESE practice.