Few studies have followed immigrant-origin individuals from adolescence to adulthood or examined their spousal choices. Using longitudinal data from Add Health, we present a life-course model that examines the differences in racial assortative mating between children of immigrants and non-immigrants. The results reveal substantial variation in racial endogamy from generation to generation. Racial endogamy was highest in the third generation, but this is due entirely to high racial endogamy among whites. Out-marriage was most pronounced among first- and second-generation immigrants. Our life-course approach shows that the effects of race and generation on intermarriage were mediated by family background (e.g. language proficiency and residence) and educational attainment (at time of marriage), a finding largely indicative of processes of marital assimilation that unfold over time and generation. Evidence of acculturation and structural assimilation, however, could not fully account for the large, persistent, and uneven effects of race and generation on interracial marriage.