This article addresses the central question of why China and the European Union (EU), two players of growing importance in global governance, cooperate on some issues of conflict resolution, but fail to do so on others. Although much discussion is devoted to their respective strategic orientations and policy preferences in world affairs, more deep-rooted factors like norms and values should also be taken into consideration. This article follows a social constructivist approach to explicate how international norms have shaped the convergent and divergent actions of China and the EU in two empirical cases: the Iranian nuclear issue and the Syrian civil crisis. It argues that because China and the EU had both internalized the international norm of multilateralism, they could cooperate in pushing for a political solution to the Iranian nuclear issue through multilateral negotiations, and take a similar approach to the Syrian civil crisis. However, whereas China has seriously questioned the ‘responsibility to protect’ as a legitimate norm, the EU has embraced and promoted it. Consequently, the two took divergent actions in the second case. It is suggested that China and its Western partners closely engage each other in constructive communication to promote mutual understanding, and ultimately expand the basis of their common norms.