The Mediterranean diet (MD), despite its multiple benefits, presents low levels of adherence among children. Moreover, childhood is a key stage in the acquisition of healthy habits. The aim of this study was to describe adherence to MD in school-age children from Asturias, Spain, and to evaluate the association with weight status and several lifestyle behaviors. A cross-sectional study was conducted on 309 children aged between 8 and 13 years old. The level of adherence to MD was evaluated through the KIDMED questionnaire. Descriptive analysis and logistic regression models were used to analyze the association between adherence to MD and weight status, frequency of out-of-school exercise, frequency of school canteen attendance, and sleep habits. We found that 54.4% of children had optimal adherence to MD and 29.9% of the sample was overweight or obese. Frequency of exercise practice was positively associated with optimal adherence to MD (95% CI: 1.02, 1.33). A positive association was found between some KIDMED items and frequency of out-of-school exercise practice and attendance at the school canteen. This study shows the need for an improvement in the adherence to MD in youth considering the concomitant occurrence of other related healthy behaviors.