This chapter explores the role EU loyalty may play with regard to the free trade agreements (FTAs) of new generation concluded by the EU and its Member States as mixed agreements. In so doing, it uses the Singapore Opinion as a case study to illustrate the position taken by the Court of Justice thereon. In order to develop such an analysis, the chapter is structured as follows. After a brief introduction on the nature and the role of the principle of loyal cooperation within the EU legal order, the next section carries out a general assessment of its implementation in the EU external action. Section 3 analyses the implications in terms of EU loyalty emerging from the Singapore Opinion. This is followed in Section 4 by some general conclusions. The analysis suggests that the approach adopted by the Court in the Singapore Opinion is consistent with the maximalist attitude so far expressed by Luxembourg judges towards loyalty as far as mixed agreements are concerned. Such an approach is perfectly in line with the attempt of the Court to strengthen the autonomy of the EU legal order vis-à-vis the international law system, an attempt which is clearly visible in the ‘generous’ reconstruction of the EU exclusive competences under the envisaged EU-Singapore agreement, as well as in the solution offered to regulate the interplay between that agreement and the pre-existing bilateral investment treaties concluded by Member States with the third country. However, the chapter argues, also thanks to the analysis proposed by AG Sharpston in her opinion in Singapore, that a change of attitude by the Luxembourg judges is not only possible, it is also needed, in order to preserve the ‘full mutual’ nature of the loyalty principle, as well as the prerogatives that still characterize the Member States’ position within the EU legal order.