A 9-year evaluation of hypertensive patients receiving antihypertensive therapy, using Cox proportional hazards regression models, found that higher Healthy Eating Index-2015 (HEI-2015) and Dietary Approaches to Stop Hypertension (DASH) scores were associated with a lower risk of cardiovascular disease (CVD) mortality, whereas higher Dietary Inflammatory Index (DII) scores were linked to an increased risk. Diet quality was assessed using participants’ 24-hour dietary intake data. Notably, greater adherence to the DASH diet demonstrated protective trends against cardiovascular mortality. These findings highlight the critical role of healthy, anti-inflammatory dietary patterns in improving long-term cardiovascular outcomes among patients undergoing hypertension treatment.