Why do Green parties perform better in European Parliament (EP) elections than in national parliament elections? Even in countries that use proportionally representative voting systems for both national and EP elections, many Green parties gained more than twice the proportion of EP seats in 2019 compared to the previous national election. Using national and EP election results, European Social Survey data, and Eurobarometer polling from the 2019 EP election, I test competing theories of Green party success. As EP voter issues become more salient and more voters believe that their vote matters to EU policy, I find that the “second-order election” effect is less relevant. Surprisingly, I also find that the Greens are the only small party family that consistently gained more representation in the EP. Different voter priorities and party issue framing, for both environmental and pro-EU issues, boosted the Green vote in the 2019 EP election
