Attempts to explain the rise in women's age at marriage across Africa have focused mainly on determinants in the urban environment, notably women's education and the economic recession. In our study, we examined the migration of adolescent girls as a factor in the transition to a later age of marriage in rural Mali, using an analysis of data from a longitudinal survey conducted over 20 years. The findings show a close correlation between the rise in labour migration and the onset of this nuptiality transition. Continuing changes in marriage patterns include not only its postponement but also a breakdown in the marriage formalization process. Two main mechanisms are documented: a direct one, as migration enables young women to choose the timing of their marriage and is a source of empowerment; and an indirect one, as migration challenges family marriage conventions and contributes to elders disengaging from control over marriage and young people.