Following the swift demise of the state-socialist regime in 1989, a profound transformation of family and fertility patterns has taken place in the Czech Republic. Family formation has been postponed and period fertility rates have fallen to very low levels, especially among young adults. Unmarried cohabitation has become relatively widespread and marriages have been progressively delayed or even foregone. These rapid shifts in family-related behaviour were primarily driven by a period change and resulted in a sharp discontinuity in cohort patterns of union formation and childbearing. We argue that the rapid change in family-related behaviour after 1990 was driven by a fundamental shift in the constraints and incentives for childbearing, which was conducive to later and more carefully planned family formation. The rapidity of observed changes can be explained as the outcome of a simultaneous occurrence of several factors, especially the expansion of higher education, the emergence of new opportunities competing with family life, increasing job competition, rising economic uncertainty in young adulthood, and changing partnership behaviour.