The EU and Japan have traditionally differed significantly in their regional security perceptions and strategies. The EU considers nationalism to be the main threat to regional security and sees regional integration as a core security strategy. In contrast, Japan remains focused on China and North Korea as traditional great power threats with the US as its main security guarantor as part of the American spoke-and-hub system in Asia. Japan has only recently started to think in regional security terms. Accordingly, bilateral cooperation between the EU and Japan on regional security remains limited with occasional cooperation within regional fora such as ASEAN and the ASEAN Regional Forum. Yet this chapter argues that Japan needs to adapt to the changing security landscape, and the EU needs to include Japan in its promotion of regional security efforts. Their shared roles as ‘civilian’ or ‘normative’ powers in international politics should provide a basis for such closer collaboration in regional security.