Diarrheal disease remains a leading cause of child death globally, especially in low and middle-income countries. Use of oral rehydration solution (ORS) for treatment of diarrhea in children, a very cost-effective intervention, remains below 50% in many countries. Here we use a multi-level longitudinal model to reveal important predictors of ORS use at the national level. The findings suggest that increasing government effectiveness along with increased implementation and affordability of community-based health programs can lead to substantial increases in ORS use. Key informant interviews with national health leaders in countries that significantly improved ORS coverage support these quantitative findings.