In this article, we study how potentially conflicting forces of socioeconomic modernization and enduring language barriers influenced one of the most intimate acts of social interaction: marriage. In the period during which Belgium underwent social and economic modernization – often thought to have diminished barriers between social groups, increasing the likelihood of social heterogamy – linguistic barriers remained strong. The intriguing question is, what happens if socio-economic modernization coincides with persistent linguistic cleavages. We will study this by looking at marriage formation in communities in the province of (contemporary) Flemish Brabant and the Brussels Capital Region. We ask: How large were the temporal and municipal variations in homogamy by social status in the period 1821–1913? And can modernization and the existence of linguistic divisions explain these variations? We use two types of data: couple data from civil registration records in Flemish Brabant 1821–1913 (N = 333,729), and, for some analyses, context data on the municipality at the time of marriage to a shorter period, 1859–1910, and thus a lower number of marriages (N = 270,151). We find that during modernization a shift took place from homogamy on fathers’ status to homogamy on groom’s status, and we find partial support for the effect of language barriers.