The notion that Europe is forged in a crisis, coined by Europe’s founding father Jean Monnet, is widespread within scholarly work on European integration. Yet, the effect of existential threats on public opinion has received little attention. This paper seeks to understand how public preferences for international cooperation and organization are shaped by existential threat perceptions. To do so, we take the EU as a case study and conduct a pre-registered vignette experiment in five EU MS on the threat of climate change. More specifically, we prime perceptions of external threat based on the coastline flooding projections for major cities. Our findings demonstrate how public preferences for international organization and collaborations are not only shaped by external threats to one's national state, but also by information on the vulnerability of another EU member state. As such, we not only contribute to the study of EU integration, but also provide new insights to the emerging literature on public support for international organizations and the on-going work on the consequences of threat perceptions for political preferences.