Background: The aim of this study was to relate adherence to the Mediterranean diet (MedDiet) to the prevalence of metabolic syndrome (MetS) in an elderly population from the north of Spain. Methods: We carried out an observational, descriptive, cross-sectional, and correlational study involving 556 non-institutionalised individuals aged 65 to 79 years. The MEDAS-14 questionnaire score was used to define the degree of adherence to the Mediterranean diet. The diagnosis of MetS was conducted using the International Diabetes Federation (IDF) criteria. Results: In 264 subjects with an average age of 71.9 (SD: ±4.2), 39% of whom were men, 36.4% had good adherence (score ≥ 9 in MEDAS-14), with no differences by gender or age. The prevalence of MetS was 40.2%, with 47.6% in men and 35.4% in women (p < 0.05). The prevalence of MetS was 2.4 times more frequent among individuals who consumed less than two servings (200 g) of vegetables daily compared with those who consumed two or more servings of vegetables daily (OR: 2.368, 95%CI: 1.141–4.916, p = 0.021). Low adherence to the MedDiet (MEDAS-14 score ≤ 8) was associated with an 82% higher prevalence of MetS (OR: 1.817, 95%CI: 1.072–3.081, p = 0.027). Conclusion: An inverse relationship was established between adherence to the MedDiet and the prevalence of MetS.