This article examines the ways in which sustainability discourses intersect with carceral policies. Building new prisons to ‘green’ industry standards; making existing prison buildings less environmentally harmful; incorporating processes such as renewable energy initiatives; offering ‘green-collar’ work and training to prisoners; and providing ‘green care’ in an effort to reduce recidivism are all provided as evidence of ‘green’ strategies that shape the experience of prisoners, prison staff and the communities in which prisons are located. Although usually portrayed positively, this article proposes an alternative, potentially more contentious, interpretation of the green prison. In the context of mounting costs of incarceration, we suggest that green discourses perversely are fast becoming symbolic and material structures that frame and support mass imprisonment. Consequently, we argue, it may be the penal complex, rather than the environment, which is being ‘sustained’. Moreover, we suggest this is a topic worthy of attention from ‘green criminologists’.