Over the last decades car sharing has been recognized as a socio-technical innovation that can help to reduce or replace the use of fossil-fueled private cars in urban regions. To understand how car sharing may be used in the future, and its potential role as a driver of a more sustainable mobility system, studies of early user practices represent an important source of knowledge. Based on a combination of inductive statistical techniques and qualitative investigations of car-sharing households in Oslo, this study explores emerging practices of car sharing. A survey of 1,136 active car sharers is combined with 36 in-depth interviews with households using three different car-sharing schemes. The results suggest that car sharing is developing as three different proto-practices, labeled as active green, local flexible and long-distance holiday. These three practice forms relate to variations in car-sharing schemes, type of travel, and length/frequency of trips, as well as to affiliated motives and meanings. The study contributes a deeper understanding of how current car-sharing practices are emerging in households and the potential implications for sustainable urban mobility and policy developments.