Abstract: While much of the urban sustainability debate often focuses on technical systems and the built form the purpose of this paper is to explore the role of social capital – the social structure, networks and relationships within a community of people - in moving towards sustainability. It is these social aspects that are overlooked or misunderstood by developers and not valued by financial institutions and the market. Inner urban eco-communities can offer important insights in terms of design, materials and technologies, and the practice of living in ‘community’. Drawing on social capital theory, and using qualitative ethnographic research undertaken at two Australian inner urban ecocommunities as part of a doctoral thesis (in progress), this paper explores the ways that social capital is enacted in these eco-communities and how such mechanisms impact the movement towards sustainability.