.Laparoscopic One-Anastomosis Gastric Bypass (OAGB) is a bariatric procedure that combines the principles of restriction and malabsorption, which are achieved by creating a long and narrow gastric pouch and bypassing part of the small bowel (duodenum and part of the jejunum). It is currently the third most common bariatric procedure worldwide; more than19,000 operations (4.8%) are performed per year. OAGB is synonymous with "Mini Gastric Bypass" and "Omega Loop Gastric Bypass". There are numerous technical variants for performing OAGB and organizing pre- and postoperative care. This article is based on the approach to bariatric surgery at the Department of General Surgery at Vienna Medical University. We focus on patient preparation before a bariatric/metabolic procedure with mandatory and optional examinations to decrease the patient's risk and find the procedure best suited for each individual patient. Next, the surgical technique itself is described, including positioning of the patient, positioning of the trocars and related tips, tricks, and technical highlights, as well as the specifics of the postoperative course. OAGB is an effective procedure for weight loss and remission of comorbidities with a low risk of malnutrition for patients with good compliance. For OAGB to be successful, important technical steps such as a long and narrow pouch, exact length of the biliopancreatic limb and hiatoplasty, if necessary, should be taken. In terms of post-operative care, regular check-ups are vital to ensure a positive outcome in long-term follow-up and the early detection of adverse developments.