It is a common assumption that through decades of co‐operation there has been an emergence of trust between the Member States of the European Union. Yet, we have little evidence about the nature of trust and its implications for decision‐making, in particular in times of crisis. Hence, our article's central question: how does trust matter in the process of decision‐making during crisis? Our argument is that uncertainty during the crisis enabled trust‐building between the actors: Member States and European institutions. In the case of the Ukrainian crisis, this happened in parallel to the decreasing levels of trust in EU–Russia relations. Consequently, the EU was able to agree and implement the instruments of coercive power. To illustrate our argument, we look at the adoption of EU sanctions in reaction to the annexation of Crimea, the downing of the Malaysian Airlines MH17 plane and the war in Donbass.