Traditionally, the discipline of International Relations (IR) assumed a state-centric perspective. However, as new actors emerged and begun to play an increasingly important role in international politics, the discipline opened itself towards non-state actors. Among these, multinational enterprises (MNEs), their participation in public-private partnerships and their changing role expressed in extended corporate social responsibility (CSR) have caught the interests of scholars as MNEs are no longer simply the object of regulation, but rather become political actors themselves. In a nutshell, regulation of MNEs has changed to regulation together with MNEs. Despite these changes, however, private business actors in general and CSR in particular have predominantly been investigated from rationalist perspectives. Although a fertile and dynamic theoretical field, constructivism has been surprisingly reluctant to deal with MNEs. To counter this reluctance, the paper conceptualises MNEs as "social actors" affected by norms and acting on a logic of appropriateness. This theoretical argument is empirically illustrated by analysing the arguments given by MNEs for participating in CSR. Besides the expected logic of business reasoning in corporate speeches, ideas and arguments such as moral and ethical obligations, changed understandings of the corporate role in society and the will to tackle important global issues can be found in most speeches presenting MNEs as sensitive towards social expectations. As the case of CSR shows, there is an ideational motivation for corporate action beyond rational calculation and expected consequences, indicating that corporate action itself is more complex than rationalist theories commonly suggest.