The purpose of this study is to examine how cohabiting partners’ plans to marry after the birth of their child were associated with marriage realization or continued cohabitation when their child was 1, 3, and 5 years old. Possible parents’ gender differences, couple agreement, and the longitudinal associations were examined. Using four waves of data from the Fragile Family and Child Wellbeing Study, results from logistic regressions showed that (1) the majority of cohabiting mothers and fathers had plans to marry their partner after the birth of their child; (2) in general, mothers’ plans to marry were significantly associated with couples’ marriage realization whereas fathers’ were not; (3) agreements between partners in their marriage plans were associated with marriage realization. Other relational and demographic characteristics were also considered. Research and clinical implications of the findings were discussed.