The Russian invasion of Ukraine in February 2022 has had profound effects on the stability and security of Europe. This study examines the attitudes of Europeans toward the European Union (EU) in the aftermath of the invasion of Ukraine. Using Special Eurobarometer data collected between February and April 2022 with a representative sample of the EU (N = 26,502), it leverages the quasi-experimental setting with the coincidence between the timing of the invasion and the fieldwork period of the Eurobarometer. Our findings indicate a general increase in support for the EU in the aftermath of the invasion by 4 percentage-points (11 percent of a SD). While the amplitude of the effect remains similar, we see larger treatment effects as more days passed after the invasion. We also observe significant variation at the individual level in treatment effects, particularly by ideology, with left-leaning individuals being more critical of the EU following the invasion. In general, our research demonstrates the significant impact of regional conflicts on public attitudes toward supranational organizations such as the EU and highlights the role of the EU as a provider of security and stability in the face of such conflicts.