This article attempts to provide an answer to the puzzle of how to account for the variations in levels and effectiveness of security cooperation between the EU and China, particularly given the apparently structural nature of the main factors affecting their security relationship. The hypothesis put forward in this study is that normative differences and overlaps could hold explanatory value in this regard, on the basis of theoretical premises grounded in social constructivism. To this purpose, the article contributes a detailed discussion of the normative positions held, respectively, by the EU and China, particularly with regard to definitions of threats and priorities, positions on national sovereignty and non-interference, and views on multilateralism and multipolarity. The impact of these normative positions is illustrated and discussed with reference to some salient cases of EU–China security cooperation, such as the Iranian nuclear issue, the ratification of the CTBT, and anti-piracy operations in the Gulf of Aden. While underlining the importance of norms as an explanatory variable, the article also points to the relevance of the interplay between norms and interests, as well as their interaction with other structural factors—particularly the role of the United States as the main security actor in international affairs.