Background and Objectives: Weakly acidic reflux has been reported as the major cause of symptom occurrence in patients with proton pump inhibitor (PPI)-refractory non-erosive reflux disease (NERD). This study is aimed at clarifying whether the pH value of weakly acidic reflux affects the induction of symptoms. Methods: We retrospectively evaluated the records of combined multichannel intraluminal impedance and pH monitoring in 57 patients with PPI-refractory NERD. Weakly acidic refluxes were divided into 3 categories based on the pH value of the refluxate: pH 4-5, 5-6, and 6-7. Results: A total of 29 patients were positive in the symptom index. The symptom provocation rate in reflux of pH 4-5 (19%) was much higher than in that of pH 5-6 (11%) and pH 6-7 (12%). In the reflux at pH 4-5, the symptom provocation rate in the proximal reflux was higher than that in the distal reflux (p < 0.05), whereas the reflux at pH 5-6 and pH 6-7 was not significantly different in the symptom provocation rate between the proximal and distal refluxes. Conclusion: Reflux at pH <5 reaching the proximal esophagus was the main factor in the induced symptoms of patients with PPI-refractory NERD.