Climate change and urban development patterns amplify the risks of flooding and water pollution. While climate-robust stormwater management has the potential to reduce these risks, its implementation remains slow. Enhanced and new forms of collaboration between municipalities and property owners are proposed as the keys to advancing the volume and effectiveness of such measures. However, the practical outline of new collaborative practices between these actor categories within existing built urban environments is still in its early stages. This study uses the experiences and visions of respondents from eleven municipalities and six property companies in Sweden to start examining the challenges, needs, and requirements for such forms of collaboration. The study identifies current challenges, including ambiguous legislation, organizational differences, unclear roles and responsibilities, and weak economic incentives. Requirements for improved collaboration opportunities include overcoming perceived legal obstacles, assigning collaboration coordinators, establishing long-term collaborative forums, and clarifying financial principles and cost-sharing arrangements. Creating the conditions for collaboration thus requires changes in formal national frameworks, as well as changes in local organizational structures, norms, and traditions.