Three years into the Decade of Education for Sustainable Development, there has been considerable discussion regarding education for sustainable development (ESD) at a policy level, yet very few countries and communities have moved to integrate ESD into their educational curriculum. In this article we argue that the conceptualization and implementation of ESD can be advanced by grounding it in the human capability approach. We define "education for sustainable human development" as educational practice that results in the enhancement of human well-being, conceived in terms of the expansion of individuals' agency, capabilities and participation in democratic dialogue, both for now and for future generations. We conclude that incorporating Amartya Sen's human capability approach as the basis of ESD will provide the clarity of direction and purpose needed for the transformation of curriculum, pedagogy and assessment.