openConcerns regarding effective governance in the realms of environmental protection and sustainability have taken centre stage in the EU as already reflected in the Commission’s 2001 White Paper, advocating for new modes of governance. This thesis explores the potential of network governance as an instrument for green governance in the EU. Existing literature has examined this mode of governance from various angles, but inconclusive results persist, along with the lack of comprehensive comparative studies. The present work aims to bridge this gap by conducting an in-depth analysis of the EEAC Network and the EIONET. The overarching goal is to contribute to the understanding of the nature of networks and their effectiveness in EU sustainability governance. Taking a mixed-method qualitative approach using semi-structured interviews and document analysis, this study looks at the networks’ structures and decision-making processes, as well as the functions they perform. Despite marked structural and governance differences between the EEAC Network and the EIONET, common factors influencing their behaviour become apparent, including central steering roles, resources, national institutional set-ups, participant engagement, and EU-level policy and global developments. Examining contributions and limitations on how networks promote EU environmental policy objectives related to sustainable development, this research highlights the importance of communication and trust, stakeholder inclusion, flexibility, access to decision-makers, goal consensus, and the aggregation and use of knowledge and resources. These insights enhance our comprehension of the role of networks in EU sustainability governance, shedding light on both potentials and associated challenges