Research has found that married individuals who cohabited only once before marriage with their future spouse (i.e., “spousal cohabiters”) have a distinctive financial advantage: they accumulate more wealth over time than individuals who married without ever cohabiting (i.e., “directly married”). Using the National Longitudinal Survey of Youth 1979 and growth curve models, the present study attempts to identify the source of spousal cohabiters’ wealth advantage. We find that marriage is associated with gains for financial and nonfinancial wealth, increasing home equity, and decreasing debt over time. Spousal cohabiters begin marriage with more debt than the directly married. Conditional on education, income, and other key factors, spousal cohabiters pay down their debt faster and generate greater home equity over time thereby accumulating more wealth than the directly married. This pattern of financial behavior among spousal cohabiters explains some, but not all, of their financial advantage over married persons who never cohabited prior to marrying. Given the increasing prevalence of cohabitation among young adults, these results offer important insights into the long-term economic outcomes associated with premarital cohabitation.