Migration scholars have long regarded the trajectory of the third generation as a critical test of assimilation; however, scholarship to date has been limited and largely focused on socioeconomic attainment. In this article, we rely on a large dataset of adolescent respondents in England, Germany, and the Netherlands to compare the second and third generations in terms of their social networks and cultural identities. The third generation shows stronger ties to the native fourth-plus generation alongside weaker ties to coethnics. We document comparable, albeit more moderate, dynamics of assimilation over generations in regard to national and ethnic identification, along with substantial variation by country of destination and ethnic origin group. Our results point to a dominant trend of assimilation at the third generation and suggest future challenges to provide a more durable assessment of postwar migration waves two generations after settlement.