Mutual trust in European Union law traditionally refers to a horizontal relationship between Member States, requiring them to consider ‘all the other Member States to be complying with EU law’, as the European Court of Justice has repeatedly stated. This Article considers a new perspective: is it possible to detect the existence of trust between Member States on one hand and the European Union’s institutions on the other hand? If so, what are its legal manifestations? And what light does trust shed on the cooperation between the peoples of Europe? To answer these questions, the Article seeks to offer a synthetic vision of the case law, selecting legal issues of European integration as examples of ascending (from Member States to the EU) and descending (from EU to Member States) trust. It then discusses reasons why the Court of Justice of the European Union may want to create a relationship of trust with Member States, drawing from the fruitful insights of political psychology.