Background: In Islam, a child is a trustee of a parent who has been given by Allah SWT, the child has the right to education, one of which is sex education (Supriatna, 2010). As a good educator, parents will look for an effective alternative method in providing children’s education. that children can achive good maturity. Objective: To know the level of parental knowledge about the method of giving sex education in Islam to preschoolers in Tamantirto Yogyakarta. Research Methods: The type of this research is descriptive quantitative with sample of 196 parents from 6 institutions of early childhood with stratified random sampling technique. Analysis using descriptive in the form of frequency and percentage. Results: The results showed that the level of knowledge of parents about the method of giving sex education in Islam in preschool children in good category as much as 161 respondents (82.1%), and in enough category that is 35 respondents (17.9%). Conclusions and suggestions: Most parents are categorized well in the knowledge of the method of giving sex education in Islam to preschoolers so that the researcher suggests that further research tries to increase the range of respondents studied to ensure accurate results.