Background and objectives A Mediterranean lifestyle may prevent and mitigate cardiometabolic disorders. We explored whether adherence to a Mediterranean lifestyle was prospectively associated with the risk of metabolic syndrome (MetS) among coronary heart disease (CHD) patients. Methods The Coronary Diet Intervention with Olive Oil and Cardiovascular Prevention (CORDIOPREV) study was an interventional diet study to compare a Mediterranean diet with a low‐fat diet, in 1002 CHD patients. The Mediterranean lifestyle (MEDLIFE) index was used to assess adherence to a MEDLIFE at baseline, and after 5 years, in 851 participants from the CORDIOPREV study. Subjects were classified as having high (>13 points), moderate (12–13 points), and low (<12 points) adherence to the MEDLIFE. Multivariable logistic regression models were used to determine the association between MEDLIFE adherence and the risk of MetS development or reversal. Results During the 5‐year follow‐up, CORDIOPREV participants with high adherence to MEDLIFE had a lower risk of MetS development (odds ratio OR 0.37, 95% confidence interval CI 0.19–0.75, p < 0.01) and a higher likelihood of reversing preexisting MetS (OR 2.08 CI 95% 1.11–3.91, p = 0.02) compared with participants in the low MEDLIFE adherence group. Each additional one‐point increment in the MEDLIFE index was associated with a 24% lower risk of MetS development (OR 0.76, 95% CI 0.64–0.90, p < 0.01) and a 21% higher likelihood of reversing preexisting MetS (OR 1.21 CI 95% 1.04–1.41, p = 0.01). Conclusions Our results showed that greater adherence to a MEDLIFE reduced the risk of subsequent MetS development and increased the likelihood of reversing preexisting MetS among patients with CHD at baseline.