A 4-year-old boy presented with vomiting, abdominal pain and a visible swelling on the left side of the upper abdomen. He had been generally unwell for a week, and had been suffering from constipation for a longer period of time. Radiological examination revealed a large space containing air and fluid in the left side of the upper abdomen and the chest region. During surgery, gastric volvulus and an elevated diaphragm were found. Plication of the diaphragm was performed, and the intra-abdominal organs were replaced in their correct positions. Patient recovered well and remained without complaints. Diaphragm relaxation is rare, and can be either congenital or acquired. Unlike congenital diaphragmatic hernia, diaphragm relaxation is characterised by an elevated diaphragm which, although intact, is hypoplastic.