Background: Brazil's fertility transition was the result of multiple socioeconomic transformations that started during the second quarter of the 20th century. Education expansion played an important role in this process by promoting changes in social norms and in assortative mating profiles.

Objective: The goal is to estimate cohort fertility rates (CFR) of women in union by educational pairing (different combinations of men’s and women’s educational levels) and whether changes observed in assortative mating profiles were associated to the Brazilian cohort fertility transition.

Methods: First, we estimate CFR by educational pairings for women cohorts born between 1925 and 1969. Second, we decompose the difference in CFR between younger and older cohorts into two components, the effects of changes in the composition of educational pairings (structural changes) and the rate effects (other factors).

Results: The CFR of couples in Brazil declined from levels higher than 6 children per women for cohorts born in 1925–1929, to less than 3 children for women born in 1965–1969. Changes in the composition of educational pairing corresponded to approximately one-third of these reductions in cohort fertility.

Conclusions: These results suggest that changes in the composition of educational pairing related to the rising education levels of men and women corresponded to an important share of the cohort fertility decline of women in unions.

Contribution: The evaluation of the Brazilian fertility transition through the lens of cohort fertility and educational pairings may provide new insights and methodological alternatives for assessing fertility transition in countries that rely on censuses as the main data source for fertility estimation.