We develop a model of immigrant political action that connects individual motivations to become politically involved with the context in which participation takes place. The article posits that opinion climates in the form of hostility or openness toward immigrants shape the opportunity structure for immigrant political engagement by contributing to the social costs and political benefits of participation. We argue that friendly opinion climates toward immigrants enable political action among immigrants, and facilitate the politicization of political discontent. Using survey data from the European Social Survey (ESS) 2002 to 2010 in 25 European democracies, our analyses reveal that more positive opinion climates—at the level of countries and regions—increase immigrant political engagement, especially among immigrants dissatisfied with the political system. However, this effect is limited to uninstitutionalized political action, as opinion climates have no observable impact on participation in institutionalized politics.