Reductions in the environmental impacts of everyday life are increasingly accepted as a crucial part of any transition to a sustainable economy. Despite profound differences in how it should be achieved, the vast majority of recent research on such pro-environmental action recognises that it poses a fundamentally social challenge - demanding shifts not merely in individuals' attitudes and behaviours, but also in social norms, contexts and practices. Despite this general acceptance of the social nature of the problem, however, to date there has been very little attention paid to perhaps the most basic social medium: social interaction. To address this gap, the paper applies some of Erving Goffman's concepts to an ethnographic case study of a pro-environmental change initiative called Environment Champions. The analysis reveals how interaction processes can both help and hinder the spread of pro-environmental acts, and thus calls for them to be given further attention in future research.