This paper uses data on individual political opinions from the European Social Survey to study the role of horizontal cultural transmission on immigrants' political assimilation in Western Europe. We analyze five key political issues: redistribution, gay rights, EU integration, immigration policy and trust in political institutions. Controlling for individual socio-economic characteristics, we document that immigrants show identical support for redistribution as natives, display more conservative attitudes towards gay rights and more liberal views on the other three issues. These differences widen with the cultural and religious distance between immigrants' background and Western European norms, and decrease with the number of years since migration. Among immigrants that have spent at least 10 years in their host country, attitudes towards migration policy catch up with those of natives and the migrant-to-native gap on political trust is reduced by 80\%. In contrast, differences on EU integration and gay rights remain stable while immigrants' views on redistribution becomes relatively more conservative. These attitude-specific patterns are also salient when studying political preferences at the regional and sub-regional level. Our results strongly point towards the transmission of cultural values from natives to immigrants on matters of immigration policy and political trust, whereas attitudes towards redistribution seem immune to cultural influences at destination.