Seeing the sociopolitical system as fair and legitimate is important for people’s participation in civic duties, political action, and the functioning of society in general. However, little is known about when migrants, without life-long socialization in a certain system, justify the sociopolitical system of their host country and how system justification influences their political participation. We examined antecedents of system justification using a survey among Iranian migrants in eight European countries (N = 935). Subsequently, we examined the relationship between system justification and political participation intentions. We found that system justification beliefs are generally high in our sample, mainly stemming from an assessment of opportunity to achieve changes in intergroup relations. Stronger social identity threat, feeling disadvantaged, a longer residence in Europe, and perceived intergroup stability all relate to less system justification. Conversely, stronger efficacy beliefs bolster system justification. Furthermore, we found some support for a curvilinear relationship between system justification and political participation intentions, but the size of this effect is small. The results show that the high levels of system justification of Iranian migrants are at risk when discrimination and disadvantage are perceived to be stable facets of society. Surprisingly, political participation to better Iranian migrants’ societal position is barely affected by system justification. We discuss implications and further research that can increase understanding of system justification among migrants.