Some scholars have hypothesized that social integration in the European Union (EU) is a trigger for bi-national European marriages. Although this idea has been the motivation behind some research, empirical evidence shows that the effect of accession to the EU has had a limited effect on partner choice. This study aims to add to the knowledge on this issue by analysing the trends and patterns of marriages between Portuguese and non-Portuguese citizens between 1997 and 2011. We conducted bivariate and multivariate analyses using official data on marriages that took place in Portugal, with the results showing that bi-national European marriages remained stable throughout the period, although some nuances are evident depending on the type of marriage. While Portuguese-EU15 marriages declined over time, those between native Portuguese and other Europeans increased. Gender differences determined the development and composition of these marriages. This article also notes the existence of three distinct types of bi-national union: labour, recomposed and highly educated couples. The final part of the article seeks to explain and interpret the findings, specifically by focusing on the increase in cohabitation as a functional substitute for bi-national European marriage, the need to compare and combine the number of marriages in both spouses’ countries, and changes in the structure of the Portuguese matrimonial market due to the arrival of new social groups (e.g. Brazilian and Eastern European).