Objective: The objective of this study is to evaluate serum magnesium levels, dietary magnesium intake, and their relation ships with hypertensive complications in adults with hypertension (HT). Materials and Methods: Patients with HT for ≥10 years were divided into two groups for evaluation. Although the casegroup comprised 34 patients having at least one of the hypertensive complications of atherosclerosis, heart failure, and renalfailure, the control group comprised 34 patients with HT without complications. In addition to demographic information,anthropometric measurements (body weight, height, waist circumference [WC]), and medical information of the patients were collected, dietary information was acquired via a three-day food record. Results: Dietary magnesium intake was similar in both the groups; however, both values were below the recommendeddaily intake. The case group had significantly lower serum magnesium level than the control group. We found no correlationsbetween serum magnesium and dietary magnesium intake level. Low serum magnesium level was a possible risk factor forcomplications (OR: 9.02, 95% CI: 3.00–27.10). Serum magnesium concentration was negatively correlated with the dura tion of HT, WC, fasting blood glucose; however, it positively correlated with the estimated glomerular filtration rate. Althoughthe mean body mass index levels were similar, the mean WC was higher in the case group than in the control group. Conclusion: In conclusion, this study’s results clearly showed insufficient dietary magnesium intake and lower serum mag nesium levels in patients with hypertensive complications. Serum magnesium level was also found to be correlated with someparameters closely related to the complications of HT