This article applies the insights of social practice theory to the study of proenvironmental behaviour change through an ethnographic case study (nine months of participant observation and 38 semi-structured interviews) of a behaviour change initiative — Environment Champions — that occurred in a workplace. In contrast to conventional, individualistic and rationalist approaches to behaviour change, social practice theory de-centres individuals from analyses, and turns attention instead towards the social and collective organization of practices — broad cultural entities that shape individuals’ perceptions, interpretations and actions within the world. By considering the planning and delivery of the Environment Champions initiative, the article suggests that practice theory provides a more holistic and grounded perspective on behaviour change processes as they occur in situ. In so doing, it offers up a wide range of mundane footholds for behavioural change, over and above individuals’ attitudes or values. At the same time, it reveals the profound difficulties encountered in attempts to challenge and change practices, difficulties that extend far beyond the removal of contextual ‘barriers’ to change and instead implicate the organization of normal everyday life. The article concludes by considering the benefits and shortcomings of a practice-based approach emphasizing a need for it to develop a greater understanding of the role of social interactions and power relations in the grounded performance of practices.