Weight loss maintenance is crucial for obesity management, yet optimal dietary patterns for this period are not established. We aimed to explore the relationship between adherence to the Mediterranean diet and weight loss maintenance. Sample includes 565 adults (62 % women) of the MedWeight study. Eligible volunteers were those reporting intentional weight loss of ≥10 %, starting from a BMI ≥ 25 kg/m2, over 12 months prior to enrolment. Based on current weight, participants were characterised as maintainers (≤90 % maximum weight) or regainers (>95 % maximum weight). Socio-demographics and weight history were recorded. Dietary intake was assessed by two non-consecutive 24-h recalls within 10 d and analysed in energy, macronutrient and food group intakes. Adherence to the Mediterranean diet was assessed with the Mediterranean Diet Score (MedDietScore) (range 0–55, greater scores showing higher adherence). Protein intake was higher in maintainers than in regainers (P < 0·001). When MedDietScore quartiles were considered, a linear trend for weight loss maintenance was revealed (P < 0·05). After adjustment for basic demographic characteristics, being in the third or fourth quartile of the MedDietScore (v. first) was associated with 2·30 (95 % CI 1·29, 4·09) and 1·88 (95 % CI 1·10, 3·22) increased odds of maintenance. Regarding individual MedDietScore components, only fruit intake is associated with increased odds for maintenance (1·03 (95 % CI 1·01, 1·06)). The leave-one-out approach revealed that at least six MedDietScore components were essential for the observed relationship. Higher adherence to the Mediterranean diet was associated with 2-fold increased likelihood of weight loss maintenance. Future studies should replicate these findings in non-Mediterranean populations as well.