Objectives: Although serum sodium (sNa) is regarded as a predictor for cardiovascular disease, cardiovascular mortality, and all-cause mortality, whether serum sodium is a predictor for coronary artery calcification (CAC) in chronic kidney disease (CKD) remains unclear.  Methods: We prospectively enrolled 1832 CKD patients with hypertension and excluded ones with hypernatremia (mean age: 55.0 years, male 1148 [62.6%]) who had sNa and coronary computed tomography as part of the Korean Cohort Study for Outcomes in Patients With Chronic Kidney Disease at baseline. CAC score of > 0 Agatston unit (AU) and > 400 AU were defined as presence and severe CAC, respectively. Results: Participants were divided into sodium groups as follows: 664 in Group 1 (142.0-144.9 mmol/L), 670 in Group 2 (139.1-141.9 mmol/L), 411 Group 3 (136.1-139.0 mmol/L), 87 Group 4 (≤136 mmol/L). There were 339 (51.0%) in Group 1, 366 (54.6%) in Group 2, 224 (54.5%) in Group 3, and 55 (63.2%) in Group 4 of patients with presence of CAC, respectively. There were 68 (10.2%) in Group 1, 90 (13.4%) in Group 2, 53 (12.8%) in Group 3 and 24 (27.5%) in Group 4 of patients with severe CAC, respectively. sNa levels were not associated with presence of CAC (adjusted odd ratio [OR] 1.11, confidence interval [CI] 95% 0.91-1.35, P=0.299).  However, decrease in sNa level were associated with for severe CAC (categorical variable: reference Group 1, adjusted OR=1.21; 95% CI 1.02-1.45, P=0.027; continuous variable: adjusted OR=0.93; 95% CI 0.87-0.99, P=0.048) even after adjustment including age, sex, diabetes mellitus, presence of coronary artery disease or peripheral vascular disease or cerebrovascular disease, glomerular filtration rate, urine protein to creatinine ratio.  Conclusions: Lower sNa even within the normal range was associated with the severe CAC in non-dialyzed CKD patients with hypertension. However, sNa levels are not associated with presence of CAC.