Introduction: The rates of bariatric surgery have increased significantly in Australia over the past 25 years, mirroring a trend seen in most other developed countries and reflects the increasing prevalence of obesity. A rare complication of thoracic and upper abdominal surgery is iatrogenic diaphragmatic hernia. This report outlines the presentation, work-up, and management of a rare case of an iatrogenic parahiatal hernia four years after a one-anastomosis gastric bypass (OAGB) procedure. Presentation of Case: A 51-year-old female presented with left back pain that was worse on inspiration. She had previously undergone gastric band removal with conversion to OAGB. A CT scan of the chest and abdomen revealed a parahiatal hernia containing over 50% of the remnant stomach. The hernia was managed laparoscopically with reduction of the stomach, primary suture repair and reinforcement with a biosynthetic mesh. Post-operatively, her pain resolved, and her recovery was uncomplicated. Discussion: Iatrogenic diaphragmatic hernias are uncommon but are important to recognise intra-operatively at the time of injury and remain a consideration post-operatively as a differential diagnosis for atypical symptoms. They should be repaired in most cases due to the risk of developing severe complications including incarceration. Parahiatal hernias present an anatomically interesting subtype, between the fibres of the left crus and the left pillar of the right crura, which otherwise part caudally at T12 at the aortic hiatus. Conclusion: The case outlines a rare complication of a parahiatal diaphragmatic hernia after bariatric surgery. This complication deserves consideration due to the severe outcomes that can occur if left untreated.