Research on child custody primarily focuses on the well-being of children following divorce. We extend this literature by examining how the prospect of joint child custody affects within-marriage investment in children through changes in household bargaining power. Variation in the timing of joint-custody reforms across states provides a natural-experiment framework with which to examine within-marriage investment in children. The probability of children's private school attendance declines by 12% in states that adopt joint-custody laws. We also find evidence linking joint-custody reform to higher rates of labor force participation for married mothers, which may indicate less time devoted household production.