Children who show better eating practices are less likely to suffer from severe caries than those who eat a diet rich in sugars. In the present study, we aimed to establish the relationship between the severity of dental caries and adherence to the Mediterranean diet. A cross-sectional study was carried out in which 263 children aged 2 to 14 years old were examined intraorally to analyze the presence and severity of caries. Children’s parents/caregivers completed the KIDMED questionnaire to determine their degree of adherence to the Mediterranean diet. The results showed that the prevalence of caries is greater than 80% in children with medium or low adherence to the Mediterranean diet, and remains significant at 67% in the high adherence group (p = 0.010). A statistically significant negative correlation of weak magnitude (r = −0.29; p < 0.001) was found between adherence and the number of carious teeth. Caries severity in the first molars is also influenced by adherence to the diet in a statistically significant way. In conclusion, there is an association between adherence to the Mediterranean diet and the prevalence, extension, and severity of caries in the pediatric population.