Background: Many questionnaires that assess subjective symptoms or health-related quality of life (HRQOL) have been developed to confirm the efficacy of treatment in patients with gastroesophageal reflux disease (GERD). However, few reports have correlated early improvements in scale scores with predictions of subsequent therapeutic responses. Our aim was to investigate the appropriate timing for evaluating therapeutic response and subsequent changes in symptoms and HRQOL. Methods: This was a post hoc analysis of a multicenter prospective cohort study. A total of 5,279 GERD patients with Frequency Scale for the Symptoms of GERD (FSSG) scores ≥8 points at baseline were analyzed. Correlations between HRQOL and FSSG were investigated and logistic regression analysis was performed. Results: The FSSG scores and HRQOL improvements in responders were significantly greater than in non-responders. Positive correlation between FSSG and HRQOL was observed. Based on the analysis, severity of esophagitis at baseline, complications of hypertension, higher HRQOL mental score at baseline, and higher FSSG score at baseline were predictors of responders. Gastrectomy, complication of insomnia, and prior medication with proton pump inhibitors were predictors of non-responders. Conclusion: Evaluating patients’ symptoms during the fourth week of rabeprazole therapy allows predictions of subsequent changes in subjective symptoms and HRQOL.