Subnational mobilization literature has flourished since the mid. 1990s. Regional and local authorities have tried, not always successfully, to utilize alternative channels of representation in the European Union (EU) in different policy areas and with different scope and depth. The policy areas and the degree of subnational mobilization is greatly varied contingent on exogenous-at the EU level-and endogenous-within local and regional organisational capacity-factors. Most commonly, subnational authorities (SNAs) find themselves involved in cohesion policy issues, environmental affairs, and social policy measures, mostly involved in the implementation phase. However, as the EU continuously emphasizes the importance of regional and local authorities in facilitating the European integration process, it has fuelled SNAs' institutional ambitions and expanded their aspirations for participation in new policy areas, even in fields traditionally considered to be exercised-and monopolized-by national authorities, such as foreign policy issues. This article focuses on the role of subnational institutions in the European Neighbourhood Policy (ENP), a relatively new policy area compared to other established EU policies. In short, the ENP was introduced in 2004 and revised in 2011 and 2015. Its rationale is to bring closer EU countries and their neighbours, so as to work together on issues regarding prosperity, stability and security for all. The ENP constitutes a policy field for subnational authorities that aim to mobilize in the supranational arena. The European Neighbourhood Instrument (ENI-former European Neighbourhood Policy Instrument/ENPI) is the ENP financial tool which provides opportunities for "financial mobilization" to institutional actors by granting funds for implementing programmes. In addition, the European Committee of the Regions (CoR), the official assembly of representatives of local and regional authorities in the EU, stands for another channel for subnational mobilization. Through specific policy initiatives that have been established and promoted by the CoR, namely the Conference of Regional and Local Authorities for the Eastern Partnership (CORLEAP) and the Assembly of Local and Regional elected European Integration Studies 2018/12 20 Representatives from the EU and its Mediterranean partners (ARLEM), local and regional institutions have the opportunity to actively participate in the ENP. Moreover, the European Grouping of Territorial Cooperation (EGTC) serves as a distinct policy tool for enhancing territorial development and cooperation, allowing for the engagement of subnational actors from different EU countries-and third countries as well. Drawing on the literature of multi-level governance, it is argued that sub-state entities have managed to expand their institutional role in new policy areas that have been traditionally monopolized by central state authorities. Certain types of subnational mobilization originally found on initiatives proposed and developed by the CoR, the financial instrument...