It has long been argued that the legalization of same-sex marriage would have a negative impact on marriage. In this article, I examine how different-sex marriage in the Netherlands was affected by the enactment of two laws: a 1998 law that provided all couples with an institution almost identical to marriage (a “registered partnership”) and a 2001 law that legalized same-sex marriage for the first time in the world. I first construct a synthetic control for the Netherlands using OECD data for the period 1988–2005 and find that neither law had significant effects on either the overall or different-sex marriage rate. I next construct a unique individual-level data set covering the period 1995–2005 by combining the Dutch Labor Force Survey and official municipal records. The estimates from a discrete-time hazard model with unobserved heterogeneity for the first-marriage decision confirm the findings in the aggregate analysis. The effects of the two laws are heterogeneous, with presumably more-liberal individuals (as defined by their residence or ethnicity) marrying less after passage of both laws and potentially more-conservative individuals marrying more after passage of each law.