This article examines the role of party system polarization in shaping immigrants’ party loyalties in their host country. It suggests that foreign-born individuals are more likely to become partisans when political parties take more distinct policy positions on immigration control. Moreover, this relationship is more pronounced among foreign-born non-citizens than foreign-born citizens. Using individual-level public opinion data from eight rounds of the European Social Survey (ESS), 2002–2017, and measures of party system polarization constructed using party policy positions from the Chapel Hill Expert Survey (CHES) in 17 West European democracies, the analyses confirm these expectations. The findings presented here suggest that party polarization on immigration control enhances, rather than undermines, immigrant political integration in contemporary democracies.