Aim: Evaluation of parents’ knowledge about oral health in primary schools of the National Guard, Riyadh. Methods: A cross-sectional study was carried out in King Abdullaziz Iskan City. Parents of 257 school children, who completed a self-administrated questionnaire, were involved in this study. Results: It was revealed that there was a lack of knowledge and awareness of the importance of fluoride, regular dental visit, and plaque. In contrast, good knowledge about brushing and the relation between oral health and general health was observed. Also, a mother with a high level of education has knowledge better than mothers who have a low level. In addition, the families with higher income have more knowledge especially about fluoride and dental visits. Conclusion: Parents’ knowledge about the importance of oral health needs to be improved because children mostly gain knowledge about oral health and hygiene from their parents and then start establishing their habits. Coordinated efforts by dentists and other health professionals are required to impart dental health education about oral health and preventive care among parents.