A 70s man underwent minimally invasive esophagectomy and gastric conduit reconstruction via the posterior mediastinal route for early esophageal cancer 5 years ago. Three days prior to hospital visit, he presented with abdominal fullness, left chest pain, and vomiting. A CT revealed a postoperative hiatal hernia, and emergency surgery was performed laparoscopically. The laparoscopic findings showed that the transverse colon had prolapsed into the left thoracic cavity through the esophageal hiatus on the left side of the gastric conduit. The transverse colon had no sign of necrosis. The diaphragmatic defect was closed with unabsorbable suture. Increased bowel motility due to postoperative fat loss in the mesentery and intra-abdominal pressure are thought to be causes of the hernia. In addition, decreased adhesion formation due to endoscopic surgery may be a contributing factor. Although there is no unanimous opinion regarding the suture fixation of the conduit to the diaphragm after esophagectomy, it should be performed to prevent a herniation. Postoperative hiatal hernia occurs more than 5 years after the surgery is relatively rare, but its occurrence should be noted.