This article investigates the nature of the relationship between associational involvement and migrant political participation. We explore the extent to which empirical evidence supports the mechanisms proposed by four popular theories in the political participation literature: social capital, group consciousness, civic voluntarism, and mobilization theory. To do so, we employ a mediation-effect approach with data from random samples of migrants in four European cities. Our results show that associational membership mainly operates through a direct effect stressing organizations' role as agents of mobilization and that associational membership and the links that migrants forge in these associations are crucial for their political engagement. The evidence presented shows that the mobilizing role of voluntary associations — not their role in developing trust, furthering group identity, or providing skills — remains the key to understanding why such organizations spur migrant political participation.