This book assesses EU-Japan security relations, examining how they have developed in individual security sectors and how they could be affected by international developments. The conclusions of the Economic Partnership Agreement and the Strategic Partnership Agreement in 2017 demonstrate the steady growth in EU-Japan political relations. Since the 1990s, dialogues between the EU and Japan have benefitted from extensive trade and investment ties and shared liberal values. Based on collaborative research by European and Japanese scholars, this book provides an in-depth, systematic and comparative analysis of the extent to which the EU and Japan have achieved concrete actions in the pursuance of security cooperation across a range of key areas such as nuclear proliferation, regional security, international terrorism, and energy and climate security. Further, it seeks to explain why some security sectors (such as economic and cybersecurity) have resulted in more extensive EU-Japan cooperation, while others lag behind (such as military and regional security). Common declarations and actions of shared interest and concerns have often led to only modest levels of security collaboration, and the book highlights factors that may be seen as intervening between intention and action, such as the role of external actors, for instance China and the US, and the constraints of internal EU and domestic Japanese politics. This book will be of much interest to students of European security, Japanese politics, diplomacy studies and international relations.