As national governments and global institutions fail to address climate change, an increasing number of cities have committed to major sustainability and climate strategies. Why do some cities take bold action while others remain on the sidelines?Christof Brandtner shows that city climate action is not simply a matter of political will: It is an organizational problem. Cities do not act alone. They are embedded within both a broad institutional superstructure of professional networks and peer cities as well as a deep organizational infrastructure of civil society organizations, public agencies, and socially responsible firms. This dual embeddedness shapes cities’ capacity to plan, learn, lead, and scale sustainability solutions. Drawing on comparative research spanning fifteen years and thousands of cities around the world, Brandtner traces how environmental strategies, sustainability practices, and green building initiatives emerge, diffuse, and take hold. He uncovers the structural conditions that enable and inhibit meaningful climate action, revealing why it varies so widely across cities. By combining lenses from urban theory and organizational sociology, Cities in Action sheds light on how cities navigate their social and institutional environments to meet the climate challenge. This book offers a novel perspective for scholars, policy makers, and practitioners seeking not just to explain but also to empower city action.