Unhealthy dietary habits are an important risk factor for cardiovascular disease (CVD) and adopting a healthy diet is a central recommendation in CVD prevention. This study assessed the dietary habits of patients with established CVD, their compliance to dietary guidelines, and the relationship between guideline-compliance and recurrent cardiovascular event risk. 2656 patients with established CVD from the Utrecht Cardiovascular Cohort-Secondary Manifestations of ARTerial disease (UCC-SMART) prospective cohort study, were included between 1996 and 2022. Data on dietary intake was retrospectively collected for all participants in December 2022 using a 160-item food frequency questionnaire. Compliance with dietary guidelines was quantified using an amended version of the Dutch Healthy Diet 2015 (DHD-15) index (range: 0-135). Cox proportional hazard models were used to quantify the relationship with cardiovascular events (stroke and myocardial infarction). Among 2656 CVD patients (77% male, mean age 59 ± 9 years), median energy intake was 1922 IQR: 1536-2351 kcal/day. The median DHD-15 index was 81.7 IQR 71.2-92.0, with high compliance scores for recommendations on legumes and fish, and low scores for recommendations on whole grains, red meat, processed meat, and dairy. A higher DHD-15 score was associated with lower stroke risk (HR 0.78, 95% CI 0.66-0.92 per 10-point increase) but not with myocardial infarction. Compliance with dietary guidelines was suboptimal in patients with established CVD. High compliance was associated with a clinically significant reduction in stroke risk in patients with established CVD, emphasizing the importance of dietary counseling.