This report explores governance innovation and implementation strategies for engaging the private sector in climate action within the EU Cities Mission framework, emphasising multi-actor collaborations. The study examines approaches to stakeholder engagement, partnership structures, implementation processes, and private sector motivations through analysing four diverse cities: Gothenburg, Guimarães, Budapest, and Valladolid. Across these cities each highlighted innovative practices towards private sector mobilisation. Some common challenges included administrative complexity, resource limitations, engaging SMEs, maintaining stakeholder momentum, coordinating across sectors, defining clear roles, and ensuring accountability. Cities responded by adopting streamlined communication strategies, targeted financial and technical support, and adaptive governance mechanisms. The report concludes that successful multi-actor collaborations depend on strategic frameworks, clear mutual benefits, adaptive governance practices, and strong institutional leadership. Next steps could include include capacity-building, simplified engagement processes for SMEs, policy alignment, structured monitoring, and institutionalised collaboration frameworks to effectively sustain private sector participation in urban climate governance.