Data from a longitudinal study were used to examine differences among couples that cohabited before engagement, after engagement, or not until marriage. Survey data and objectively coded couple interaction data were collected for 136 couples (272 individuals) after engagement (but before marriage) and 10 months into marriage. At both time points, the before-engagement cohabiters (59 couples) had more negative interactions, lower interpersonal commitment, lower relationship quality, and lower relationship confidence than those who did not cohabit until after engagement (28 couples) or marriage (49 couples), even after controlling for selection factors and duration of cohabitation. Our findings suggest that those who cohabit before engagement are at greater risk for poor marital outcomes than those who cohabit only after engagement or at marriage, which may have important implications for future research on cohabitation, clinical work, and social policy decisions.