RATIONALE AND OBJECTIVE: The Mediterranean diet (MeDiet) has beneficial effects on cardiovascular risk factors. We analyzed the association between adherence of a MeDiet in patients with type 2 diabetes mellitus (T2DM) and levels of HbA1c. PATIENTS AND METHODS: This was a cross-sectional study in individuals with T2DM participating in the PREDIMED trial at the centre of Pamplona. Information on diet was collected with a validated 14 point scale of adherence to the MeDiet and blood samples were obtained to assess HbA1c levels. RESULTS: We studied 383 participants with T2DM, 53.4% women (mean age 69 ± 6 years). HbA1c data were available in 262 cases (mean 6.9 ± 1.5%). Although there was a potential inverse non-significant association between adherence to MeDiet and HbA1c levels after adjusting for age and sex, it was not statistically significant. Multivariate analysis additionally adjusted for physical activity, smoking, time of evolution of the T2DM, body mass index and insulin treatment found similar findings (OR = 0.69, 95% CI 0.17-2.83). CONCLUSIONS: Although we found not enough evidence to support that a MeDiet is associated with lower levels of HbA1c in patients with T2DM, our results suggested an inverse trend. Future studies with larger sample size are necessary.