Child support enforcement policies enjoy widespread support from legislators because most people believe that fathers should support their children, even when they live in separate households. Less often emphasized is the potentially far-reaching impact of these policies on increasing the bargaining power of women. This paper examines the relationship between child support enforcement and bargaining power among married and cohabiting couples. A simple economic bargaining model predicts that living in a state with stricter child support enforcement increases the bargaining power of married mothers, who can more credibly threaten divorce. The effect on cohabiting mothers is less clear because enforcement increases a father’s incentive to marry, which potentially increases his bargaining power within a cohabiting union. Using the Fragile Families and Child Wellbeing Study, we find evidence that living in a state with stricter child support enforcement increases the bargaining power of married mothers, but reduces the bargaining power of cohabiting mothers. Furthermore, among mothers who were cohabiting at birth, only those who marry the father after the birth are better off in stricter states. In contrast, mothers who remain in cohabiting relationships or who break-up with the father are significantly more likely to be depressed, worried, and experience hardship in stricter enforcement states.