The most effective long-term treatment for severe obesity is bariatric surgery with improvement or resolution of obesity-related comorbidities. Single-anastomosis procedures including single-anastomosis duodenoileal bypass and one-anastomosis gastric bypass are relatively new procedures that are gaining popularity worldwide. These surgical techniques are perceived to be less complex with a shorter learning curve in comparison to the standard biliopancreatic diversion with duodenal switch and Roux-en-Y gastric bypass; however, long-term outcomes and complications remain controversial. This article aims to review one-anastomosis procedures, evaluate their outcomes, and review potential complications.