This study aimed to examine how views on marriage and cohabitation changed between 2004–2009 and 2020–2023 in Austria, Czechia, Estonia, Germany, and Norway. Cross-sectional data from the first round (GGS-I) and the second round (GGS-II) of the Generations and Gender Survey were analyzed using linear regression models, with attitudes toward marriage and attitudes toward cohabitation as dependent variables. The study focused on attitudes of 48,246 individuals aged 21–45 (20,284 from GGS-I and 27,962 from GGS-II). The results revealed a substantial shift toward positive views on marriage in Czechia and Estonia, with people considering it less outdated over time. In Austria and Norway, there was a less pronounced shift toward negative and neutral views on marriage. The acceptance of cohabitation was already high in most countries in the first round and increased between rounds in Germany and Austria. Czechia remains the most traditional out of the five countries when it comes to both attitudes toward marriage and cohabitation. A weak gender difference in attitude toward marriage was found in Norway and Estonia, with women viewing marriage as an outdated institution less often than men. The study shows how attitudinal changes differ across institutional contexts and challenges the expectation of the Second Demographic Transition framework of a universal shift away from traditional family arrangements.