We use data from Wave 3 of the Mexican Family Life Survey (N = 7276) and discrete-time regression analyses to evaluate changes in the association between educational attainment and timing to first union across three generations of women in Mexico, including a mature cohort (born between 1930 and 1949), a middle cohort (born between 1950 and 1969), and a young cohort (born between 1970 and 1979). Mirroring prior research, we find a curvilinear pattern between educational attainment and timing to first union for women born between 1930 and 1969, such that once we account for the delaying effect of school enrollment, those with the lowest (0–5 years) and highest levels of education (13+ years) are characterized by the earliest transition to a first union. For women born between 1970 and 1979, however, we find that the pattern between education and first union formation has changed. In contrast to their peers born in earlier cohorts, highly educated women in Mexico are now postponing first union formation relative to the least educated. We draw on competing theories of educational attainment and timing to first union to help clarify these patterns in the context of Mexico.