BACKGROUND: One-anastomosis gastric bypass (OAGB) is the third most common metabolic/bariatric procedure worldwide. A point for discussion regarding OAGB is acid and non-acid reflux in mid- and long-term follow-up. The aim of this study was to objectively evaluate reflux and esophagus motility by comparing pre- and postoperative results of 24-h pH-metry, high-resolution manometry (HRM), and gastroscopy. SETTING: Cross-sectional study and university hospital based. METHODS: This study includes primary OAGB patients operated at the Medical University of Vienna before 31st December 2022. After a mean follow-up of 4.1 ± 2.9 years, the preoperative examinations were repeated. Additionally, history of weight, remission of obesity-related complications (ORC), and quality of life (QOL) were evaluated. RESULTS: A total of 50 patients were included in this study and went through all examinations. Preoperative weight was 125.5 ± 21.0 kg with a BMI of 44.6 ± 5.4 kg/m CONCLUSION: This study has shown decreased rates of acid reflux and increased rates of non-acid reflux after a mid-term outcome of primary OAGB patients. Gastroscopy showed significant signs of chronic reflux exposure of the anastomosis, the pouch, and the distal esophagus, even in asymptomatic patients. General follow-up visits in patients after OAGB should be considered.