This article discusses whether Japanese military and political elites perceived the Soviet Union and the People’s Republic of China (PRC) as threats during the Cold War. Realist scholars have argued that Japan’s security alliance with the United States and the global balance of power were such that most Japanese officials did not perceive either of the Communist giants as a serious military threat. Reaching a similar conclusion but for starkly different reasons, constructivist scholars have argued that cultural, normative, and identity factors explain why Japanese elites did not perceive the Soviet Union or China as militarily threatening. Neither of these arguments holds up. Archival data and oral history collections from Japan’s Self-Defense Force and National Diet Library reveal that Japan’s defense establishment and political leaders perceived both the Soviet Union and the PRC as extremely threatening and that these perceptions fluctuated in intensity over time, across sectors, and among actors. Psychological factors, including affect, behavioral tendencies, and cognitive beliefs (the ABC model), may better explain why Japanese judged the intensity and source of perceived threats in the manner that they did. These findings underscore why threat perception in the international system is best evaluated by aggregating individual judgments and their distribution among larger groups.