Metabolic acidosis is common in chronic kidney disease (CKD) and may have various deleterious consequences. Arterial stiffness in CKD patients is associated with poor cardiovascular outcomes. The present study aimed to evaluate the association between serum bicarbonate and arterial stiffness using the baseline cross-sectional data set of a large-scale Korean CKD cohort. 2,238 CKD patients were enrolled in the KoreaN Cohort Study for Outcome in Patients With Chronic Kidney Disease (KNOW-CKD) from 2011 to 2016. The present study was conducted on 1,659 patients included in this cohort with baseline serum bicarbonate and brachial-to-ankle pulse wave velocity (baPWV) data. Metabolic acidosis was defined as a serum bicarbonate level of <22 mmol/L, and baPWV was used as a surrogate of arterial stiffness. Mean serum bicarbonate was 25.8 ± 3.6 mmol/L. 210 (12.7%) patients had metabolic acidosis. baPWV was significantly higher in patients with metabolic acidosis (P < 0.001) and showed a significant inverse correlation with serum bicarbonate (Unstandardized β -16.0 cm/sec; 95% CI -20.5, -11.4; P < 0.001) in an unadjusted model, which was retained after adjustment (Unstandardized β -5.4 cm/sec; 95% CI -9.9, -1.0; P = 0.017). Metabolic acidosis was found to be associated with a high baPWV in pre-dialysis CKD patients.