Young children living in poverty in low- and middle-income countries are more likely to experience undernutrition, infectious diseases, environmental contaminants, and unstimulating surroundings. Exposure to such risks during the first 1,000 days of life leads to significant inequalities in a child’s developmental trajectory. Child-focused water, sanitation, and hygiene (WASH) interventions have the potential to help create improved environmental conditions that are necessary for children to thrive. The current study examined the effects of a low-cost, easily scalable child-focused WASH intervention (targeting children ages 0-3) that was delivered in a single session to caregivers in Laos, a lower-middle income country in Southeast Asia. Our results suggest that even a brief, single-session of a child-focused WASH intervention can produce short-term measurable effects on caregiver and child outcomes, especially when combined with a similarly efficient responsive stimulation intervention.