Introduction: Magnesium is an essential element that has numerous biological functions in the cardiovascular system. Hence, three hundred patients with known cardiovascular disease above the age of 25 years were studied to evaluate association between dietary and serum magnesium with cardiovascular risk factors. Materials and Methods: Patients were divided into three groups according to serum magnesium levels; ≤1.6 (Group 1), >1.6-2.6 (Group 2) and: >2.6 mg/dl (Group 3), and into two groups according to dietary magnesium intake; ≤350 mg/day (Group 1) and >350 mg/day (Group 2), respectively. Results: Mean age of patients was 60.97 ± 12.5 years. Total cholesterol, triglycerides, VLDL, and LDL were significantly higher and HDL cholesterol significantly lower in group 1 when compared with group 2 and group 3. Diabetes, dyslipidemia, and hypertension were negatively correlated with serum magnesium levels; which were maintained even after adjustment with age, sex, and anthropometric parameters in multiple regression analysis. Similar observations were observed in dietary magnesium intake except LDL and total cholesterol. Dietary magnesium was positively correlated with serum magnesium. Conclusions: Hypomagnesaemia and low dietary intake of magnesium are strongly related to cardiovascular risk factors among known subjects with coronary artery disease. Hence, magnesium supplementation may help in reducing cardiovascular disease.