In Europe, historically sensitive borders may entail conflicts but also showcase good examples of cross-border cooperation. It is the case of the borderland between Austria’s Federal State Tyrol and Italy’s Autonomous Region Trentino-South Tyrol. These territories used to form the County of Tyrol until the end of World War I, yet they now belong to two different states following Trentino-South Tyrol’s annexation to Italy in 1919. Nonetheless, relations between these sub-state entities never ceased to exist; they have rather evolved into cross-border cooperation, which embodies a special instance of horizontal intergovernmental coordination across state borders. This case study shows how the Land Tyrol and the Provinces of Bolzano/South Tyrol and Trento succeeded in institutionalising cross-border cooperation despite the lack of support—or even opposition—from national authorities. Particularly, two elements stand out as key factors for success: the strong political commitment at the regional level and the opportunity provided by the European Union (EU) to enhance cooperation through the EU’s dedicated legal tool—the European Grouping of Territorial Cooperation.