A 70-year-old woman presented to the emergency department with symptoms of a lower respiratory infection. A chest x-ray showed enlargement of the mediastinal space. The patient was admitted with a respiratory tract infection and started on antibiotic treatment. A computed tomography (CT) scan of the thorax revealed a large diaphragmatic hernia with stomach, large intestine and caudal pancreas lodged in the thoracic cavity. After the antibiotic treatment, the patient became asymptomatic and surgery repair was declined. Morgagni hernia is an uncommon type of congenital diaphragmatic hernia, which may be asymptomatic until late in life or may be present acutely with life threatening conditions. LEARNING POINTS Morgagni hernia is the most rare form of congenital hernia, representing 2 to 3% of all cases. Chronic respiratory symptoms or gastrointestinal disturbances can be the only manifestation. Most asymptomatic cases in adults are found after doing chest x-ray for unrelated problems.