This article investigates the role of practices in sustainability transitions. Employing a social practices approach, we analyze the reproduction of car-sharing practices and discuss its role in transitions to sustainable mobility. We assemble data from interviews with 39 households using car sharing in Oslo, Norway, and show three specific ways of reproducing car-sharing practices: (a) FUSS: Frequent, Unplanned, Short-term, and Small-car use, (b) POLL: Planned, Occasional, Longer-term, and Larger-car use; and (c) PERC: Purpose Elected from Range of Cars. After examining contributing factors, especially the role of provider and user contexts, we turn to how car sharing relates to other household practices. We highlight how cardependent activities and substitutes for daily car use contribute to the reproduction of carsharing. We then discuss how the reproduction of a new practice can help to explain the process through which a niche-based practice becomes a regime-based practice in the transition from one mobility regime to a new one. The article shows that by understanding the reproduction of practices as several different performances, a social practices approach can contribute to understanding the normalization of new mobility practices in sustainability transitions.