The purpose of this study was to determine the relationship between the environment and the incidence of diarrhea in children under five in the working area of ​​the Nogosari Public Health Center, Boyolali Regency. This research method uses an observational design with a cross sectional approach. The subjects of this study were housewives who had toddlers and had suffered from diarrhea with a population of 328 people. The results showed that there was a relationship between drinking water sources (p = 0.001), latrine ownership (p = 0.018), type of house floor (p = 0.001). 0.036) with the incidence of diarrhea in children under five and there is no relationship between the physical quality of clean water (p = 0.307) with the incidence of diarrhea in children under five