BackgroundDiarrheal disease kills over half a million people each year in sub-Saharan Africa; the majority are children under 5 years. About 58% of diarrhea cases are associated with poor water, sanitation, and hygiene—a critical issue for people living in informal settlements. In Kenya, 60% of Nairobi’s population lives in informal settlements; yet, there is a paucity of research exploring the relationship between water, sanitation and hygiene (WASH) conditions in these settlements and associated health outcomes.MethodsThe study examines characteristics of women’s WASH behaviors and environments as potential factors associated with household diarrhea in Mathare Valley Informal Settlement in Nairobi using cross-sectional survey data collected from 550 women.ResultsApproximately 17% of participants reported that at least one member of the household suffered from diarrhea in the previous 2 weeks—48% of the cases were children under five. Results from a logistic regression exploring factors associated with reports of household diarrhea suggest that women’s sanitation management strategies are associated with recent household diarrhea. Women who use toilets for defecation during the day, but rely on bags, buckets, or open defecation (OD) for urination during the day and for urination and defecation at night have over five time the odds of recent household diarrhea than women who use a toilet for all their sanitation needs. The odds of diarrhea were also higher for participants who walk up to 2 min to reach their toilets/sites for defecation and those who rely on water from taps inside buildings and plots. Odds were 62% lower for participants with clean toilets.ConclusionsFindings suggest that health targets to reduce the prevalence of diarrheal diseases in informal settlements may not be met unless particular attention is paid to the needs of women living in these environments.