The European Union (EU) is nowadays a hot issue in national politics. As a result of years of intense crises, such as the Eurocrisis, the refugee crisis or the war in Ukraine, the EU has become an object of contestation in national parliaments. Existing studies have unveiled that mainstream political parties adopt pro-EU views, whereas extremist political parties defend anti-EU stances. How national parliamentary discourse on the EU affects public opinion, however, remains unknown. Often, individuals have very little knowledge about the EU. Evidence demonstrates that EU politics are perceived as more complex and technical than national politics. Parliaments, the biggest arenas for deliberation and communication, can contribute to disseminating information and arguments that foster individuals to formulate their political preferences. Thus, the national parliamentary discourse can, arguably, influence public opinion on the EU. We analyse how the national parliamentary discourse shapes EU public opinion by looking at parliamentary speech data and individual-level data from eight EU countries between 2000 and 2021. The findings suggest that the tone of radical right parties on EU topics influences how citizens perceive the EU. This effect is moderated by the salience of EU speeches by radical right parties and individuals' ideological self-placement. The results also suggest that the tone of radical left parties on EU topics does not influence EU public opinion formation.