Cities are increasingly seen as having an important role in tackling societal challenges related to climate change, while open innovation is increasingly accepted as a new way of working for governments. In the current work, we explore the role of open innovation to tackle global challenges on a city level. In the context of the city of Rotterdam and its vision on sustainability and liveability, seven collaborative initiatives are introduced. These initiatives aim to address both sustainability and liveability goals. Our research shows that in order to have these initiatives contribute to the overall municipal goal on sustainability and liveability, the municipality needs to take different roles. Whereas traditional open innovation literature usually distinguishes three main types of open innovation, namely outside-in, inside-out, and coupled processes, the current study shows that open innovation for sustainability in the city needs a much more fine-grained and elaborate perspective; a multi-level open innovation model that allows for different co-creative partnerships joining forces in sustainability challenges. It can be concluded that governments have a key role in infrastructuring these co-creative partnerships.