Diarrhoea is one of the primary causes of mortality in under-five-children in developing regions. Poor sanitation practices and the consumption of water from unsafe sources contribute to the prevalence of this preventable disease among children. This study aimed to investigate the factors associated with poor sanitation and drinking water facilities and their contribution to diarrheal-related infections among children in South Africa, utilizing data from the 2019 General Household Survey. This quantitative study employed chi-square and logistic regression analyses to examine the relationships among sanitation variables, water-related variables, and health outcomes, while accounting for demographic and socioeconomic factors. The study found that 3.3% of children under-five experienced diarrhoea within three months preceding the survey. Key factors associated with diarrheal prevalence included age, racial group, and poor handwashing practices. Logistic regression analysis revealed that handwashing practices were the strongest determinant. Handwashing after using the toilet was significantly associated with a reduced prevalence of diarrhoea. The study underscores the urgent need for health education initiatives that improve hand-washing practices to reduce diarrheal-related infections among under-five children in South Africa. Addressing poor sanitation practices and consumption of unimproved drinking water through targeted interventions could significantly lower diarrheal-related deaths and improve public health outcomes.