Background: Mediterranean diet adherence (MDA) is declining globally, yet comprehensive national data on Moroccan adolescent dietary patterns remain scarce. Objective: The present study aimed to assess MDA and analyze urban-rural disparities among Moroccan adolescents. Material and Methods: This cross-sectional national study recruited 3600 adolescents aged 10-18 years (2160 urban and 1440 rural) across Morocco’s 12 administrative regions. The Mediterranean Diet Quality Index for children and adolescents (KIDMED) was used to assess MDA; a structured questionnaire was additionally administered to collect sociodemographic and anthropometric data. The nutritional status was assessed using body mass index-for-age z-scores according to World Health Organization (WHO) standards. Multiple logistic regression identified factors associated with poor adherence. Chi-square tests were conducted to examine differences in Mediterranean diet dietary behaviour classes by location and sex. Results: Mean KIDMED score was 4.55 ± 3.51. Poor adherence (≤ 3) was found in 38.66%, medium adherence (4-7) in 38.80%, and optimal adherence (≥ 8) in 22.50%. Urban adolescents showed significantly higher adherence than rural counterparts (5.36 ± 3.54 vs. 3.33 ± 3.08; p < 0.001). Rural residence was associated with a 3.12-fold higher odds of poor adherence (adjusted OR = 3.12, 95% CI: 2.69-3.62; p < 0.001). Urban-rural disparities were more pronounced among females (2.24 points) than males (1.67 points). Fish consumption demonstrated the largest geographical disparity (41.30% vs. 27.40%; p < 0.001). Conclusions: The present study reveals a critical urban-rural inequality in MDA: optimal adherence was achieved by only 22.50% of adolescents nationally, and was more than three times lower in rural (9.65%) than urban (31.10%) settings. Rural residence was the strongest independent determinant of poor adherence. These findings call for geographically targeted, school-based policies integrating both nutritional education and structural improvements in food access infrastructure, particularly in rural Morocco.