BACKGROUND: Antireflux mucosectomy, a new endoscopic treatment for gastroesophageal reflux disease, consists of endoscopic mucosal resection at the esophagogastric junction. This study aim was to evaluate the medium-term efficacy of the antireflux mucosectomy technique for patients with severe gastroesophageal reflux disease symptoms (proton pump inhibitor treatment-dependent or proton pump inhibitor treatment-resistant gastroesophageal reflux disease). METHODS: Between January 2017 and June 2018, 13 patients with severe gastroesophageal reflux disease without hiatal hernia, with positive pH reflux, were included in this monocentric prospective pilot study. The primary outcome was clinical success, defined by improvement evaluated by the Gastroesophageal Reflux Disease Health Related Quality of Life Questionnaire at 24 months. Secondary outcomes were technical success, decreased use of proton pump inhibitors, patient satisfaction, and adverse events. RESULTS: Thirteen patients [females = 8 (62%)], mean age 59 (range, 54-68), were included. The antireflux mucosectomy procedure had technical success in all patients. At 24 months, for 11 patients, gastroesophageal reflux disease symptoms were significantly improved, and mean gastroesophageal reflux disease score decreased from 33 (range, 26-42) to 3 (range, 0-7) (p = 0.001). Ninety-one percent ( = 10) of patients had a lower proton pump inhibitor intake at 24 months. One patient had 3 endoscopic balloon dilatations for EGJ stenosis, two patients had melena ten days after procedure, and seven patients had thoracic or abdominal pain. Patient's satisfaction at 24 months was 81%. CONCLUSIONS: In patients with severe gastroesophageal reflux disease, despite occurrence of several short-term adverse events, antireflux mucosectomy seemed effective in improving gastroesophageal reflux disease symptoms at 24 months. This trial is registered with ClinicalTrials: NCT03357809.