The Mediterranean diet (MD) is a model of a healthy diet and healthy lifestyle. Adherence to the MD has been correlated with a reduction in many metabolic disorders including cancers. The factors associated with adolescents’ adherence to the MD in North Lebanon using the KIDMED index have never been explored. Therefore, we thought to examine these factors amongst a sample of them. A cross-sectional survey was conducted in the city of Tripoli, North Lebanon. A total of 798 adolescents aged 11–18 years were randomly selected to participate in this study. All participants completed a questionnaire assessing adherence to the MD (KIDMED index), physical activity (physical activity questionnaires for older children and adolescents), health-related quality of life (KIDSCREEN-27 index) and sociodemographic characteristics (age, sex, grade level and parents’ educational status). Anthropometric measurements, including weight, height and waist circumference, were also collected. Adherence to the MD was good amongst only 13·3 % of the adolescents. The prevalence rate of overweight and obesity was elevated, affecting 36·9 % of the students. Lower adherence to the MD was significantly correlated with skipping meals (P = 0·001). Meanwhile, adolescents who were engaged in a high level of physical activity, those who consumed more meals with their families and those who benefited from better physical well-being had a better diet quality (P < 0·001). Nutrition intervention programmes, as well as public health policies, would be of interest in order to improve diet quality amongst Lebanese adolescents.