Purpose: We prospectively evaluated the association between quality of plant-based diets and 10-year first fatal/non-fatal cardiovascular disease (CVD) incidence. Methods: ATTICA study was conducted in the greater metropolitan Athens area, Greece, during 2001–2002 studying men and women (aged > 18 years old) free of CVD at baseline. Follow-up CVD assessment (2011–2012) was achieved in n = 2,020 participants (n = 317 cases). Dietary assessment was based on a validated semi-quantitative paper-based food frequency questionnaire. Overall, healthful, and unhealthful plant-based dietary indices (PDI, hPDI and uPDI) were calculated through a standard published procedure. The association between plant-based indices and CVD outcome has been evaluated via Cox regression analysis. Results: The CVD event rate was 15.7% (n = 317) with a median follow-up time of 8.41 years. The highest (3rd PDI tertile) vs. lowest (1st tertile) adherence to plant-based pattern—irrespective to healthfulness of food products consumed—was inversely associated with CVD (hazard ratio (HR) 0.56; 95% confidence interval (95% CI) 0.14, 2.25) yet the CI was wide. Ranking from 1st to 2nd and 3rd hPDI tertile the CVD event rate was 6.4%, 10.5% and 16.2%, respectively (p = 0.003). Multi-variable adjusted analysis revealed that participants assigned in 2nd and 3rd hPDI tertile had 47% (HR 0.53; 95% CI 0.25–1.08) and 68% (HR 0.32; 95% CI 0.16–0.63) lower risk to develop CVD compared with their 1st tertile counterparts. Conversely, a positive association between uPDI and CVD risk was revealed in dose–response analysis (HR(per5unitsincreaseinuPDI) 1.34; 95% CI 0.95–2.37)). Conclusions: Quality of plant-based diets is important and needs to be considered, as not all plant-source foods have beneficial cardiovascular effects.