Handwashing with soap is a cost-effective way of reducing diarrheal disease mortality in children under 5. Tracking this practice among child caretakers is a challenge, as the gold standard method – structured observations – is cumbersome, costly, and conducive to over-performance. The water, sanitation, and hygiene (WASH) field needs a valid, reliable proxy to track handwashing with soap in large surveys. This proxy is crucial as the new 2015–2030 Sustainable Development Goals (SDGs) may track hygiene. Using data from the Multiple Indicators Cluster Survey (MICS) and the Demographic Health Survey (DHS) from five countries, we conducted multivariate analyses to explore an association between the presence of functional handwashing stations (HWSs), (together with needed supplies) and the likelihood of lower reports of child diarrheal disease. A limited to moderate association exists in three of the five countries considered, characterized by comparable rates of childhood diarrhea: Malawi, Sierra Leone, and Zimbabwe. The relationship was detected when controlling for potential confounding factors (other WASH elements, socio-demographic factors, nutrition practices, and immunization status) and when accounting for cluster effects. The likelihood of reported diarrhea among children under 5 increases when there is no HWS, just a handwashing device with no supplies, only water or only soap. The relationship is moderate in Malawi and less strong in Sierra Leone and Zimbabwe. No relationship was found in Ethiopia and Ghana. Further exploration of the usefulness of this proxy in other African and non-African contexts is warranted.