Recent societal developments, as well as environmental problems like global warming, demand more socially, environmentally, and economically sustainable lifestyles and dwellings. Collaborative housing describes a possible path to meet those demands by sharing spaces and goods. To determine how the concept of sharing in collaborative housing can contribute to more sustainable cities, the following research question is posed: ‘How does the concept of sharing in collaborative housing increase the sustainability of cities?’. It is explored, what the theoretical and practical impacts of sharing in collaborative housing on social, environmental, and economic sustainability are. These questions are answered by an explorative literature review and by studying two cases of collaborative housing in Vienna in detail. Collaborative housing as an umbrella term for different types in the research context is explained, as well as the scope of sustainability within the work. Furthermore, the concept of sharing is introduced in the context of collaborative housing. The findings from literature and the collaborative housing projects are reviewed for their possibility to make urban living, and therefore cities, more sustainable. Sharing in collaborative housing serves as a catalyst for more sustainable cities, not only by its presence, but also as role model and experimental space for housing and urban development projects.