The legal status of the Arctic Ocean is strongly debated, particularly in the context of security. Some argue that the Arctic Ocean is a global commons, while others deny this. Japan is currently formulating its Arctic policy, but it is uncertain about this legal definition with respect to security matters. Japan’s Arctic policy, which was publicised on 16 October 2015, will be influenced by its bilateral and multilateral relations with the Arctic and non- Arctic states. This paper considers the following three relevant issues:(1)The concept of a global commons under international law;(2)Whether or not the Arctic Ocean can be defined as a global commons; and(3)Japan’s options for its Arctic policy with special reference to security and Japan-US bilateral relations based on the Japan-US alliance. This paper concludes that the application of global commons to the Arctic Ocean would be misguided and would not resolve issues of security because the legal concept is vague and it lacks specific context and origin. In addition, Japan’s Arctic policy should be concrete and sufficiently comprehensive to face challenges within and outside the Arctic Council.