Background and Objectives: Zonulin is a molecule that has been identified as an intestinal permeability marker in recent years. Zonulin previously linked to Diabetes Mellitus, Obesity and Cardiovascular Disease but but its role in chronic kidney disease (CKD) was unclear. This study aims to investigate the relationship between Zonulin and systemic inflammation (SI), endothelial dysfunction (ED), especially renal functions, in patients with CKD. Materials and Methods: One hundred sixty-three participants were enrolled in this study. All participants were divided into two groups, patient and control groups, according to the presence of CKD (eGFR <60 mL/min/1.73m2). Results: A total of 104 patients with CKD (mean age 58.9 ±1.4) and 59 control subjects (mean age 59.0 ±1.1 ) were included, and age (p =0.934) and gender (p =0.196) were similar between the groups. In the comparison analysis, plasma zonulin levels in the CKD group (166.16 ± 53.54) were significantly higher than the controls group (143.30 ± 60.92) (p <0.001). In the correlation analysis, serum zonulin level showed positive correlation with claudin-3 (r =0.612, p <0.001), IL-6 (r =0.307,p <0.001), creatinine (r =0.313, p <0.001) and negative correlation with eGFR (r =-0.320, p <0.001) and TC (r =-0.074, p =0.047). Additionally, in linear regression analysis, zonulin level was significantly associated to eGFR, after adjustment for age and SBP (β value =-0.918, p =0.012). Conclusion: High serum zonulin levels in patients with CKD reflect increased intestinal permeability and were associated with impaired renal function. Moreover, it was thought that zonulin level could be associated with SI, but novel clinical studies were needed to elucidate its relationship with ED.