This paper offers a new framework for understanding China-Germany sister-city diplomacy through the lens of city cluster logic, enabling subnational actors to navigate complex institutional structures and networked partnerships more strategically. Drawing upon a comprehensive policy analysis and a series of 68 interviews conducted in Germany and China between 2022 and 2025, this study illuminates a notable shift in China’s urban strategic approach to its partnership with Germany. It argues that today’s China-Germany sister-city diplomacy is shaped not only by the local interests of individual cities but also by the regional dynamics of city clusters. By understanding city cluster logic, German municipalities can more effectively align agendas, leverage networks, and coordinate initiatives, thereby strengthening their engagement with Chinese cities.