Background Reflux monitoring using combined multichannel intraluminal impedance (MII) and pH-metry increases the sensitivity for identifying gastroesophageal reflux episodes. The likelihood of a positive symptom index (SI) for patients with reflux disease (gastroesophageal reflux disease GERD or nonerosive reflux disease NERD) receiving proton pump inhibitor (PPI) treatment has been used to select candidates for antireflux surgery. Little is known about the advantages of MII-pH monitoring compared with pH monitoring alone for evaluating GERD/NERD patients off PPI treatment considered as candidates for antireflux surgery or for assessing changes in MII-pH-detected reflux episodes after antireflux surgery. This study aimed to determine the additional value of MII over pH-metry alone for patients off PPI treatment before and after antireflux surgery. Methods For this study 12 patients (4 women and 8 men; mean age, 45 years; range, 27–74 years) were evaluated using ambulatory MII-pH monitoring before and 3 months after mesh-augmented hiatoplasty. Reflux events were identified by MII-pH (A) and pH-metry (B) as patients recorded symptoms on a data logger. For each symptom, a symptom index was calculated for reflux events identified by MII-pH and by pH-monitoring alone. Results Preoperatively, MII-pH monitoring identified 71.9 ± 8.4 reflux episodes, whereas pH monitoring identified only 51.0 ± 7.8 ( p < 0.05). Postoperatively, MII-pH monitoring identified 35.5 ± 6.6 reflux episodes, whereas pH monitoring identified only 19.6 ± 4.7 ( p < 0.05). The pre- and postoperative symptom index for MII-pH monitoring was higher than pH monitoring (preoperative 91.7% vs 25%, p = 0.006; postoperative 50% vs 16.7%, p = 0.012). Conclusion Combined MII-pH-metry improves the pre- and postoperative assessment of GERD patients off PPI and results in a higher symptom-reflux association.