In Indonesia, diarrhea still becomes a problem in society’s health because its morbidity and mortality are still high. The prevalence of diarrhea on toddlers is also still high and one of the diseases that cause death to toddlers. Diarrhea self- medication for children should be done appropriately, safely, and rationally, so it is expected to decrease the level of mortality and morbidity among children caused by diarrhea. Therefore, it is very important for a mother to have a good knowledge about diarrhea self- medication. This research aims at finding out the description of mothers’ knowledge level about diarrhea self- medication on children in Batur Sub- District Banjarnegara Regency. The research design used observation method and was analyzed descriptively. It was conducted in Batur Sub- District Banjarnegara Regency Central Java for three months from February to April 2019 with mothers living in Batur Sub District Banjarnegara Regency Central Java and having under 5 years old children as respondents. The sample collecting technique in this research was purposive sampling with 100 respondents. The data analysis in this research was by categorizing the knowledge level about diarrhea self- medication of the respondents into three, i.e. good, fair, and poor. The result of the research shows that the majority of the respondents belongs to the category of early teenage hood of 17- 25 years old as many as 48 people (48%). Most of the recent education of the respondents is elementary, as many as 74 people (74%), and do not work as many as 59 people (59%). Meanwhile, for the description of mothers’ knowledge level about diarrhea self- medication on children Batur Sub- District Banjarnegara Regency, the result is that there are 85 respondents (85%) having knowledge level about diarrhea self- medication categorized as fair, while there are 15 respondents (15%) belongs to good category. It can be concluded that the respondents in Batur Sub- District Banjarnegara Regency have knowledge level about diarrhea self- medication categorized as fair.