This study analyzes changes in populist discourse in the European Union over the course of the 2015 migration crisis. Populism is becoming an increasingly salient global phenomenon, particularly in the European Union, but there is little theorization regarding its development at the level of an international institution. I address two competing literatures, on the causes of populism and its impacts at the international level, and measure empirical support for both through a three-layered content, discourse and discourse network analysis of eight qualitatively coded debates on the “migration crisis” in the European Parliament. I find that although there is some harmonization between populist and institutionalist rhetoric, following the migration crisis, populist discourse becomes increasingly conspiracy-prone, as well as becoming institutionalized in far-right and center-right European political parties.