Political participation has increasingly taken unconventional forms in advanced democracies. At the same time, the traditional party systems of Europe have been upended by the recent emergence of successful niche parties challenging the status quo. While some studies have examined partisanship and protest, we still lack a theoretical framework that ties niche party voters to political protest. In this paper, I argue that niche party voters are more likely to protest than mainstream party voters, especially in cases where they are dissatisfied with the government’s representation of their positions on the issues of immigration and climate change. I then test the theory of representational deprivation, or the sense that the government is not adequately representing the issues the voter cares about, using all nine waves of the European Social Survey in Western Europe. The findings have important implications for understanding the conditions under which people engage in political protest, especially voters of niche parties.