The Mediterranean diet is often proposed as a sustainable diet model. This study aimed to evaluate the associations between adherence to the Mediterranean diet and sustainability domains in a cohort of French adults, using multiple criteria including nutritional quality, environmental pressures, monetary cost, and dietary pesticide exposure. Food intakes of 29,210 NutriNet-Santé volunteers were assessed in 2014 using a semi-quantitative food frequency questionnaire. Adherence to the Mediterranean diet was evaluated using the validated literature-based adherence score (MEDI-LITE). The associations between the MEDI-LITE and various sustainability indicators were examined using analysis of covariance models, adjusted for sex, age and energy intake. Higher adherence to the MEDI-LITE was associated with higher nutritional quality scores, better overall nutrient profile as well as reduced environmental impact (land occupation: Q5 vs. Q1: -35%, greenhouse gas emissions: -15%, and cumulative energy demand: -17%). In turn, monetary cost increased with increasing adherence to the Mediterranean diet (Q5 vs. Q1: +15%) while higher adherents to the Mediterranean diet had overall higher pesticide exposure due to their high plant-based food consumption. In this large cohort of French adults, greater adherence to the Mediterranean diet was associated with nutritional and environmental benefits, but also with higher monetary cost and greater exposure to pesticides, illustrating the necessity to develop large-scale strategies for healthy, safe (pesticide- and contaminant-free), and environmentally sustainable diets for all.