This is a summary of a case study that provides a comprehensive comparative analysis of private sector engagement in four Mission Cities—Gothenburg (Sweden), Guimarães (Portugal), Budapest (Hungary), and Valladolid (Spain)—as part of the EU’s “100 Climate-Neutral and Smart Cities by 2030” initiative. These cities are early adopters of Climate City Contracts (CCCs), which are designed to catalyze collaborative climate governance involving a broad range of stakeholders, including the private sector.