Introduction: Oral health in children is essential for their overall well-being, influencing nutrition, language development, and self-esteem. Dental caries represent one of the most prevalent chronic diseases in childhood. Objective: The objective of this study is to evaluate the association between parents’ self-perceived knowledge of oral health and the presence of dental caries in their children. Materials and Methods: A cross-sectional observational study was conducted with 1052 children aged 4 to 14 years and their parents in Quito, Ecuador. Parents completed validated questionnaires (OHIP-14, OIDP, CPQ, and OHQoL-UK) to assess their self-perceived oral health knowledge. Clinical examinations were performed to detect cavitated carious lesions. Statistical analysis included Chi-square tests and odds ratio (OR) calculations. Results: A significant association was found between lower parental knowledge and higher prevalence of dental caries in children (Chi-square = 16.245, p = 0.0062; OR = 18.18, 95% CI [1.80–183.75]). Most caries cases were found in children whose parents rated their knowledge as “good” or “very good,” suggesting a gap between perceived and actual knowledge. Conclusions: The findings highlight the need for targeted educational strategies that address both knowledge and behavioral practices in oral health, especially among parents with low self-perceived knowledge.