Objective: To evaluate the effectiveness of educational messages sent via mobile phones on prevention of dental caries in group of preschool children. Subject and methods: 100 high caries risk children aged between 3 and 5 years from both genders were randomly divided into two groups (n=50) regarding to receiving educational messages: group 1; included children whose parents received educational messages (Test group); group 2; included children whose parents didn’t receive any messages (Control group). Every 14 days the test group received educational messages via Whats Application Messenger (WhatsApp). Visible plaque index (VPI), the decayed, missed, filled (dmf) and the International Caries Detection and Assessment System (ICDAS) indices were assessed at baseline, 3-, 6- and 9-month follow-ups, while Health Literacy Scale (HEALS) and dietary habits were determined by HEALS literacy questionnaire at baseline and 9-month follow-up. Results: Educational messages increased parental HEALS scores, enhancing the oral health status of the children and controlling the severity of dental caries. Conclusions: Educational mobile messages sent via WhatsApp were effective to control the prevention of dental caries in preschool children and improving health literacy of the parents.