Background: Mothers play a basic role in the oral health of children. Aim of the study was to evaluate the effect of educational health program on mothers' knowledge and practices toward their preschool children's oral health. Subjects and methods: Research design: A quasi-experimental design was used in this study. Setting: The study was conducted at dental outpatient clinic of Benha University Hospital. Subjects: A convenient sample was used in this study, the total number of mothers of preschool children in the above mentioned setting were 60.Tools of data collection: A structured interviewing questionnaire sheet: it consisted of 4 parts used to assess: 1) the socio-demographic characteristics of mothers, 2) the dental history of the children, 3) knowledge of mothers regarding child's oral health, 4) practices of mothers regarding their children oral health. Results: of this study showed; 43.3% of the mothers aged from 20 to less than 30 years old. 55 % of them were living in rural area, and 28.3% had secondary education. As regard total knowledge of mothers regarding their preschool children oral health; before the program implementation; 47 % of them had good total knowledge scores, while after the program implementation increased to 77 % of them. Concerning to total practices of mothers regarding their preschool children oral health; 43.3 % of them were satisfactory before the program implementation and increased to 80 % after the program implementation. Conclusion: This study concluded that: Educational health program has showed a highly statistically significant effect on knowledge and practices of the mothers post program and improving their knowledge and practices regarding their preschool children oral health. Recommendations: The study recommended that: Well-designed educational health program are needed in dental outpatient clinics at large sample and further research is needed for the maintaining children oral health