The present study examined the influence of improvements to Water, Sanitation, and Hygiene (WASH) infrastructure on rates of under-five mortality specifically from diarrheal disease amongst children in fragile states. The World Bank’s Millennium Development Goals and Sustainable Development Goals both include a specific target of reduction in preventable disease amongst children, as well as goal to improve WASH. Although gains have been made, children under the age of five remain particularly vulnerable to diarrheal mortality in states identified as fragile. Increasingly, climate change is placing undue pressure on states labeled fragile due to their inability to properly prepare for, or respond to, natural disasters that further compromise WASH development and water safety. The impact of climate change upon child health outcomes is neither direct nor linear and necessitates a linkage framework that can account for complex pathways between environmental pressures and public health outcomes. The World Health Organization’s Drive Force-Pressure-State-Exposure-Effect-Action conceptual framework was used to draw the connections between seemingly disparate, and highly nuanced, environmental, and social measures. Using a multilevel hierarchical model, this analysis used a publicly available UNICEF data set that reported rates of mortality specifically from diarrheal disease amongst children age five and younger. All 171 formally recognized countries were included, which showed a decline in diarrheal disease over time when investments in WASH infrastructure are compared. As states experience increased pressure because of climate change, this area of intervention is key for immediate health and safety of children under-five, as well as assisting fragile states long-term as the move toward stability.