Background/Aims: The aim of the present study was to analyze the diagnostic accuracy of serum eosinophilic cationic protein (ECP)for eosinophilic esophagitis (EoE) and the correlation of ECP with clinical, histopathological, laboratory, and endoscopic features of EoE.Materials and Methods: Fifteen patients with EoE and 14 healthy controls were included in the study. Demographic parameters wererecorded. EoE Endoscopic Reference Score (EREFS) was calculated according to endoscopic features, and esophageal biopsies wereobtained by a single experienced endoscopist in a patient group. Serum ECP levels (μg/mL), absolute eosinophil count (U/mm3), andmaximum peak of eosinophils/high-power field in esophageal biopsies were analyzed.Results: The median age of all participants was 33.0 (min-max: 18-46) years. There were 27 (93.1%) male patients. Serum ECP levelwas significantly higher in patients with EoE than in healthy volunteers (20.4 vs. 8.8, p<0.0001). According to the receiver operatingcharacteristic (ROC) curve analysis, ECP had 80% sensitivity and 92.8% specificity to diagnose EoE with a cut-off value of 13.9 µg/mL(area under the ROC curve 0.895; p<0.0001; 95% CI: 0.725-0.978). EREFS (p<0.0001) and the presence of food impaction (p=0.04) weresignificantly correlated with ECP.Conclusion: Serum ECP is an accurate non-invasive biomarker for EoE with high specificity and sensitivity. In addition, ECP is stronglycorrelated with EREFS and the symptom of food impaction.