A 49-year-old man presented with a 2-week history of gradual onset progressively worsening left upper quadrant pain. Ten months prior, he had a laparoscopic roux-en-Y gastric bypass (LRYGBP) for severe gastro-oesophageal reflux disease and obesity. On examination, his abdomen was not distended and was soft to palpation. The haemoglobin, white cell count, liver function test, lipase and lactate were normal. An abdominal CT scan demonstrated swirl sign. Given the suspicion of internal herniation, laparoscopy was performed demonstrating only partial closure of the jejuno-jejunal mesodefect resulting in herniation of the small bowel alimentary limb. Internal herniation should be considered as a differential diagnosis in all patients with previous LRYGBP and unexplained abdominal pain, nausea or vomiting. If closure of a mesodefect is to be attempted, a running, braided, non-absorbable suture should be used as a purse-string to avoid small defects with subsequent weight and mesenteric fat loss following bariatric surgery.