In this paper, we study if (and how) living in an unmarried cohabitation alters attitudes towards divorce. Using panel data from the first two rounds of Generations and Gender Surveys from 9 countries and applying within-person attitude change models, we show that exposure to an unmarried co-residential union makes people more tolerant towards divorce, whereas exposure to marriage increases the more traditional view. We also show that not only entry to a cohabitation, but more importantly the time spent in cohabitation alters the attitude (each month of exposure contributes to a shift in attitudes). Cohabitation thus plays a dual role in the course of the Second Demographic Transition: its rise stems from more liberal attitudes and values regarding family life. Yet, experience with cohabitation also serves as a catalyst for a value change and further contributes – at the level of an individual – to a shift towards a less traditional normative standpoint.