The proposed eosinophilic esophagitis (EoE) endoscopic reference score serves to diagnose and evaluate treatment responses in EoE. Nevertheless, the validated reference score thresholds for diagnosis and treatment response in Asian patients are yet to be established. This study aims to establish these thresholds for the first time among Asian patients with EoE. Patients presenting with ≥ 15 eosinophils/high power field and esophageal dysfunction symptoms between August 2007 and November 2021 were included. Age- and sex-matched non-EoE controls were also enrolled. Baseline characteristics, endoscopic reference score features, and scores were compared between patients and controls. Among patients, endoscopic reference score features and scores, along with peak eosinophil counts, were evaluated both before and after treatment. The optimal threshold was determined based on sensitivity, specificity, and the Youden index. Overall, 102 patients were enrolled (74.5% men; mean age, 46.9 years). The mean endoscopic reference score was 2.65 and 0.52 for patients and controls, respectively (P < 0.001). An endoscopic reference score ≥ 2 was identified as the optimal diagnostic threshold for EoE (sensitivity, 0.79; specificity, 0.86; Youden index, 0.66). Post-treatment data regarding endoscopic findings and histology were available for 30 patients. Regarding histologic response, an endoscopic reference score of ≤ 3 demonstrated the optimal threshold (sensitivity, 0.95; specificity, 0.88; Youden index, 0.83). The optimal diagnostic and treatment response thresholds were determined to be endoscopic reference scores of ≥ 2 and ≤ 3, respectively. Further studies involving a larger patient cohort are necessary to validate these findings.