Adult intussusception is rare and is often not included in the differential diagnosis. Patients who have previously undergone some form of gastric bypass procedure are more susceptible. We report a case of retrograde intussusception following a Roux-en-Y gastric bypass in an elderly patient, who presented with an abdominal mass. Her initial provisional diagnosis was bowel obstruction. As the number of bariatric gastric bypass procedures continues to rise, we are likely to see more of this kind of post-operative complication. Hence, it is crucial for surgeons to consider intussusception as a cause of abdominal pain, obstruction or mass in patients who have undergone some form of gastric bypass procedure.