PURPOSE: The management of cross-border natural resources has been the focus of research in different disciplines. Nonetheless, beyond theoretical insights, empirical evidence of successful cross-border management or governance of natural resources is still limited, even in the European Union (EU), where a range of instruments are provided to foster cross-border cooperation between its Member States. This is where our paper departs, providing evidence from an example of cross-border cooperation between two Member States of the EU, Austria, and Slovenia, adding to the analytical framework to identify the drivers of successful cross-border cooperation. METHODOLOGY: Drawing from the example of the European Grouping of Territorial Cooperation (EGTC) Geopark Karawanken we evaluate the success factors and limits for transboundary cooperation encompassing different forms of cooperation. Furthermore, based on empirical evidence of workshops with local, regional, and national stakeholders, we investigate the potential of the EGTC organizational framework to provide for the successful cross-border management of water resources within the Geopark area. FINDINGS: Our analysis of project bundles, joint ventures/consortia, and EGTCs as possible forms of transboundary cooperation indicates that EGTCs have various advantages over looser forms of cooperation. Higher operational costs for the organization are contrasted by enhanced governance of transboundary activities, in accordance with legal frameworks and representation on both sides of the border. This increases acceptance and facilitates decision-making. Furthermore, it increases the potential for receiving funds in accordance with planned activities and regional requirements, while decreasing the individual financial risk for partners. The genesis of the Karawanken/Karavanke UNESCO Global Geopark (Geopark Karawanken) indicates that looser forms of organization, for instance, project bundles, enable stakeholders to get to know each other without great institutional effort. In the course of increasing integration, the organizational form can be more complex. The experience in developing transboundary, water management instruments shows that even in a more sophisticated form of cooperation like an EGTC, there are remaining obstacles in managing transboundary natural resources. Obstacles result from e.g., national laws and regulations, data standards, monitoring techniques, and soft factors such as language barriers. IMPLICATIONS: The example of the Geopark Karawanken shows that cross-border public authorities can be significantly supported with the introduction of an EGTC. Still, an EGTC tends to exclude private companies or societal actors because they cannot be active members of the Board. Exploring further options for closer integration of the private sector in Public-Private-Partnership (PPP) models may be useful to maintain the opportunity to include much-needed private skills and resources. The experience of the Geopark Karawanken suggests that EGTCs can and will be a significant form of organization in Europe for a number of activities, for example, in the field of cross-border resources, cross-border protected areas, or cross-border predicate regions. This will support the achievement of the goals of EU programs to face the climate and biodiversity crises through transnational agreements, e.g., the Green Deal or the Biodiversity Strategy. ORIGINALITY AND VALUE: This article provides a concise overview on transnational water resource management in the European Union in the context of an EGTC, and raises points for practitioners about potential challenges for the successful introduction of an EGTC. While the analysis of common experiences of various EGTCs could lead to the development of a European standard and guideline for the successful foundation of this territorial cohesion tool, this paper provides the first step, paving the road for future research.