Background: Dietary patterns, eating behaviour and lifestyle are changing in Morocco. It would be interesting to identify and evaluate this transition in its Mediterranean context. Aims: To assess adherence to the Mediterranean diet (MedDiet) and analyse associated factors in school-age children living in oasis environments. Methods: A cross-sectional survey was conducted among 3684 school-age children between May 2015 and November 2017 in Tafilalet Oasis. The mean age was 9.81 (2.13), 51.3% were girls, and 62.7% were from urban areas. Participants were recruited from public primary schools. Adherence to the MedDiet was evaluated by Mediterranean Diet Quality (KID-MED) index. Socioeconomic characteristics and anthropometric measurements were obtained. Results: Only 2.12% had a poor KIDMED index, 57.9% had an average index and 39.98% had a high index. Maternal ethnicity was associated with degree of adherence to the MedDiet. Poor adherence was seen in 2.17% of urban participants compared with 2.04% of rural participants. Participants with high income were more likely to have good adherence to the MedDiet. Low levels of parental education were more likely to result in higher levels of poor adherence. There was no significant correlation between body weight and KIDMED index. Conclusions: Most of the study population had medium to good adherence to MedDiet, but low KIDMED index was observed. Interventions and strategies should be devised for preserving and promoting healthy eating habits in this target population.