One of the key social trends of the 20th century has been the expansion of participation in education. Using detailed retrospective information from the 1981 and 2001 censuses, this paper investigates how this expansion is associated with major trends in nuptiality in Belgium. We focus specifically on the changing gender balance in education and how this is related to the likelihood and timing of marriage and to patterns of educational assortative mating. Our empirical analysis shows that marriage was getting more universal, happening at an earlier age and more often heterogamous in term of education over the cohorts born in the first half of the 20th century. In younger cohorts, when women’s levels of education caught up with men’s, the age at marriage as well as the degree of homogamy increased again. Homogamy remained dominant throughout, but while women tended to marry men who were at least as highly educated as themselves until the 1950s cohorts, in more recent cohorts, women have tended to marry men who are at most as highly educated as themselves. Hypogamy is now the second most common pattern, after homogamy. Controlling for changes in the distribution of educational attainment by applying a log-linear model, we find that part of the changes in assortative mating in Belgium may be explained by changes in mate preferences regarding education. Finally, we find that hypogamous marriages tend to be contracted at later ages than homogamous or hypergamous ones.