This paper aims to document the increase in cohabitation in the Southern Cone (Argentina, Chile and Uruguay) between 2010 and 2021, to analyze the role played in it by certain associated factors such as changes in the educational level of the population, age structure and income distribution, and to evaluate the importance of people´s preferences (in terms of ideas or values) for cohabitation versus marriage. The results suggest that the models of nuptiality identified in previous studies coexist in the region: the traditional and the modern one, while there is a convergence of the prevalence of cohabitation among social groups within countries. Furthermore, although the prevalence of cohabitation as a springboard to marriage cannot be rejected, there are indications that suggest the presence of perceptions and ideas favorable to cohabitation as an alternative form of family organization, closer to the predictions of the theory of the second demographic transition than to the postponement of the age of entry into marriage and the birth of children.