This study examines the impact of the European Union and the programmatic and policy changes in two Irish political parties, the Green Party and Sinn Féin. The Europeanization concept is the theoretical basis of the study and it is operationalized by the use of EU salience. The study is carried out by content analysis of national and European election manifestos prepared by the parties during the 2009–2020 time period. The findings showed an increased salience on the European Union in national election campaigns by both parties, and in the European Parliament elections by Sinn Féin. A process of Europeanization has taken place in both parties regarding foreign policy and issues related to external relations. The Green Party showed an increased emphasis on the European Union regarding environmental issues. This study contributes to the research on the European impact on national political parties and the increased importance of European level politics in the national systems.