This paper aims at contributing to the discussion of how to design collaborative forms for urban commons. It does so by bridging the commons field with the participatory design tradition, which has almost 40 years of experiences in exploring and reflecting on the practicalities as well as the political aspects of collaboration among actors with diverse interest. In the growing discussion about urban commons, it has been pointed out how in designing collaborative forms for their management Ostrom’s design principles might not hold, due to the difference between urban commons and traditional commons (Foster 2011, Harvey 2011). Urban commons entail an active role of public authorities and they gather participants who have different understandings and perspectives over the commons. Diversity in participants’ interests entails a higher risk for ossification, meaning that a stable management form might hinder rather than support collaboration (Daniels 2007, Foster 2011). By building on Participatory Design theory and reflecting on three cases of collaborative management forms in Malmö (Sweden), the paper discusses how the notions of commoning and agonism might be at play in the design of collaborative forms for urban commons. The notion of commoning entails to understand collective use and management of commons as a located and ongoing socio-material practice that requires the creation of management forms able to change and evolve in time in relation to the diversity of interests. The notion of agonism, on the other hand, focuses on articulating the political dimension of commoning, that entails to consider to which extent diversity is present in the collaboration and how it could be further nurtured. The paper does not provide a definitive answer to how these collaborative forms are to be designed but it stresses the importance of considering both the practicalities as well as the political aspects of collaboration.