Why are some populists on the opposition benches willing to jeopardize strategic relations with a major superpower and others not? This article explores the politicization of foreign and security policy in the Czech Republic and Slovakia through the lens of the parliamentary debates surrounding the approval of bilateral Defence Cooperation Agreements (DCAs) with the United States. Although both agreements were ratified, they sparked significant public and political controversy, particularly in Slovakia. The study offers a comparative analysis of the narratives employed by populist opposition parties—ANO in the Czech Republic and Smer-SD in Slovakia—highlighting their divergent approaches to the DCA. While ANO supported the agreement with minimal politicization, Smer-SD mobilized strong anti-Western rhetoric, aligning itself with radical right-wing discourse. The article argues that these differences stem from distinct ideological foundations and domestic political contexts, as well as from the countries’ divergent foreign policy trajectories since the early 1990s. By applying narrative analysis within the interpretative tradition, this study contributes to the understanding of how populist actors influence foreign policy discourse in Central Europe.