This is a case report of a sliding hiatal hernia with severe gastroesophageal reflux (GER) after repair of congenital diaphragmatic hernia(CDH). It was not possible to determine whether the hiatal hernia is a de novo lesion which was missed at the original operation or a consequence of overzealous repair of the Bochdalek defect at the expense of weakening of the diaphragmatic crura. This case demonstrates that a sliding hiatal hernia can be a cause of severe gastroesophageal reflux that should be managed surgically.