Abstract: The growing threats from North Korea and China, as well as heightened concerns about the long-term reliability of the United States, have led Japan to cultivate closer security relations with other regional players. Priority has been placed on Australia, India, South Korea and south-east Asian countries, yet Japan’s National Security Strategy also states that cooperation with Russia is crucial. This is controversial since the pursuit of closer ties continued despite Russia’s intervention in Ukraine and since the policy sets Japan apart from its US ally. The purpose of this article is to explain the nature, motivations and prospects of this emerging security relationship. The article’s key finding is that the Japanese security elite do not regard Russia as a significant threat since a clear differentiation is made between Russia’s actions in eastern Europe and east Asia. Additionally, cooperation is considered vital to neutralize the danger of a prospective China–Russia united front. These and related incentives have encouraged Japan to explore security cooperation with Russia, including via 2+2 meetings and search and rescue drills. However, due to a range of international and domestic constraints, Japan’s security ties with Russia are likely to remain less developed than those with other partners in the region.