Nearly four decades of the Association of Southeast Asian Nations (ASEAN)-European Union (EU) relationship have witnessed the importance of ideas and identity alongside the economic interests in shaping the behaviour of the two sides. The study takes interest in understanding the EU’s actorness and the EU as a normative actor with and within Southeast Asia through a reflectivist lens. The thesis is an attempt to provide a new perspective on a relationship commonly assessed from an economic angle. It outlines the opportunity of non-traditional security (NTS) challenges to enhance EU actorness and normative influence in Southeast Asia. Against this backdrop, the study explores the dialogue and cooperative initiatives of two regions, which attach relatively little salience to each other. The study employs a NTS lens and draws upon the case of the Asian Financial Crisis of 1997-98, the haze in relation to forest governance, the Bali bombings of 2002 and the political conflict in Aceh. The study assumes that these NTS issues can stimulate processes of threat convergence as well as threat ‘othering’. It argues that these processes enhance European engagement in Southeast Asia and contribute to shaping regional stability in Southeast Asia. Furthermore, NTS crises present situations, where norms can become unstable, contested and substituted. This allows us to better examine the EU as a normative actor. To establish an understanding of the EU’s actorness and the EU as a normative actor, the empirical evidence will focus on the threat perceptions, motivations of action and activities of the EU and its member states. For the purpose of differentiating the EU as a normative actor, the study will also include the discussion of the normative objectives and behaviours of the EU and its member states and apply a reflectivist theoretical framework. Hypothetically, NTS crises trigger external assistance and normative influence and thus, they offer an opportunity to establish a more nuanced picture of the EU in the region. At the same time, the study acknowledges that there are a variety of constraints and variables that complicate the EU’s actorness. The thesis seeks to identify and discuss these. So far, scholarly publications have failed to apply the NTS perspective systematically. This thesis provides the first monograph-length treatment of the EU in Southeast Asia through a NTS and reflectivist lens.