Despite the vast research on the deterioration of Sino-Japanese security relations, little is known about the influence of domestic changes in Japan’s institutional setting on the formulation of its security policy towards China. Until 2010, Japanese foreign policy decision-makers eschewed a direct classification of China as a threat for Japan’s traditional security in official publications of the government. However, this significantly changed when Japanese state officials defined China as a potential military threat for the first time since the normalization of diplomatic relations in 1972 in the National Defense Program Guidelines 2010. By taking advantage of Discursive Institutionalism this paper argues that a changed institutional and discursive order of Japan’s security actors triggered this shift of the representation of China in the Japanese security discourse. Through the analysis of official publications by participants of Japan’s security discourse, the elements and effects of this domestic institutional change of Japan’s security policy towards China are scrutinized and evaluated. By applying this approach to the discussion on the deterioration of Sino-Japanese security relations, this paper puts focus on the understudied field of domestic causes of foreign and security policy changes and thus contributes to new perspectives on future research on similar topics.