This study explores the extent to which changes in age-at-marriage laws are effective in curbing early marriage and, if so, whether delays in age at marriage brought about by legal changes increase women’s likelihood to participate in higher education. To answer these questions, we combine individual-level data from Demographic and Health Surveys (DHS) and Multiple Indicator Cluster Surveys (MICS) with longitudinal information on policy changes from the PROSPERED project for six low- and middle-income countries from three broad regions: Benin and Mauritania (Sub-Sharan Africa), Tajikistan and Kazakhstan (Central Asia), and Nepal and Bhutan (South Asia). We adopted regression discontinuity design to obtain estimates of the causal effect of changes in age-at-marriage laws on early marriage and educational outcomes. Our results suggest that these laws work only selectively – specifically, significant reductions in early marriage following the law implementation are observed only in two out of the six countries – yet when they work, their impact on early marriage has important implications for women’s higher-education attendance. In Tajikistan and Nepal, an increase in the legal age at marriage by one or two years, respectively, leads to a 20-60 percentage-point higher likelihood of attending some form of higher education. In light of the significant human capital gains documented in countries where laws proved to have an impact, we conclude by arguing that, in order for changes in laws to be effective, better laws must be accompanied by better enforcement and monitoring to delay marriage and protect the rights of women and girls. Adequate policy implementation and enforcement are necessary preconditions for actual change and should be the subject of greater international attention and investments.