Studies on developed countries demonstrate that an increase in women legislators leads to a prioritization in health, an increase in social policy spending, and a decrease in poverty. Women representatives could therefore improve development trajectories in developing countries; yet, currently, no cross-national and longitudinal studies explore this possibility. Using random effects panel regression, we examine the influence of women's representation on child health (one development indicator) across 102 developing countries from 1980 to 2005. Compared to countries with no women in parliament, countries meeting a 20-percent threshold experience increased rates of measles immunizations (10 percentage points), DPT immunizations (12 percentage points), infant survival (0.7 percentage points) and child survival (1 percentage point). Incremental increases in women's representation show that child health improves most in socially and economically disadvantaged countries, and in countries less integrated in the world polity. Our findings reveal the importance of increased women's representation, particularly in less developed and less globally embedded countries.