The sharing economy represents a market-driven response to the perceived inefficient resource use arising from materialism, and as such, offers the possibility of a more environmentally sustainable form of consumption. However, the sustainability benefits attributed to the sharing economy remain contentious and fraught with paradox. Drawing on a critical discourse analysis of three sharing economy brands (Lime, Rent the Runway and BlaBlaCar) we identify that sustainability discourses compete with claims arising from the espoused benefits of immateriality and platform brands’ desire for rapid growth. We identify and explore three platform brand discourses (disrupting unsustainable leaders, guilt-free choice, and non-commercial appeals) and their associated practices. In doing so we identify that tensions between these discourses and practices give rise to three sustainability-related contradictions: displacement of sustainable alternatives, hidden materiality, and creeping usage. Our findings contribute to our understanding of the sharing economy and its role in sustainability.