How does the internationalization of the workforce and increasing presence of non-standard employment relate to trade union attitudes in advanced democracies? While evidence from Europe shows that immigrant workers are significantly less likely to unionize than natives, little attention has been paid to immigrants’ attitudes towards unions despite their potential role in explaining immigrant-native unionization gaps. In this paper, we contribute to this understudied research by shifting the focus to the increasing job precarity in non-standard employment– highly concentrated among immigrant workers – and its implication on immigrants’ union attitudes. We argue that job precarity contributes to the lack of collective action and political demand towards unions among immigrants. Notably, we suggest that the distinct importance of the workplace for social and political integration among immigrants, pre-existing immigrant-specific labor market discriminations, and linkages between employment and residence status explain why job precarity has particularly detrimental effects on union attitudes among immigrants. Using data from 13 Western European countries, we show that immigrants in fixed-term contracts hold significantly more adverse attitudes towards unions than those in standard employment situations. On the contrary, we find that native workers’ attitudes towards unions are uncorrelated with the precarity of their employment status. We conclude that job precarity among immigrant workers might further explain unionization gaps as it leads to more pessimistic union attitudes among immigrant workers. Considering increasing immigration and non-standard employment, our findings highlight a crucial issue to be addressed for the future sustainability of social dialogue and industrial relations in Europe.