The paper's main objective is to establish the relationship between environmental risk factors of childhood diarrhea and its occurrence in the Korogocho slum in Nairobi County. The hypotheses to be tested were; no significant relationship between environment and external risk factors and contraction of childhood diarrhea for those younger than five years in the Korogocho slum. The study variables included treatment of and sources drinking water, type of and cleanliness of toilet facilities, and accessibility. Self-reporting and two-week recall was the data collection strategy adopted for diarrhea outcome and its determinants. The selection of households for respondents (mothers of the target population) used systematic random sampling. Every third household with a child below five years of age was selected. When there was no child in the third household, the researcher went to the next one with a child's mother below five years until the study achieved a sample size of 90 respondents. Data was collected using well designed open-ended questionnaires, and analysis used descriptive and chi-square statistics. Findings showed that community and household environmental factors positively impacted diarrhea for the target population in the Korogocho slum. However, access to and sharing toilet facilities were not statistically significant in contracting diarrhea for the sample group. Based on two weeks recall, 36.4% of mothers reported that their children within the age limit had contracted diarrhea. Based on the results, the study identified several recommendations and suggested areas for further research. The key recommendations are to institutionalize deliberate interventions to provide slum dwellers with clean and quality drinking water and proper sanitation facilities to ensure the safe and effective fecal waste disposal.