Pyopericardium is a rare condition with a high mortality rate in which infection propagates in the pericardial space, leading to a pus filled pericardial effusion and cardiac tamponade, which can cause cardiogenic shock and death. We present a case of a previously healthy woman of 52, who was admitted with a severe lower respiratory tract infection that eventually led to a pyopericardium. The diagnosis of pyopericardium was delayed due to masking of symptoms by her underlying infection, sepsis and an upper gastrointestinal bleed that the patient suffered during the admission, requiring an emergency gastroscopy. The pyopericardium was considered when ST elevation was seen on an ECG and an ECHO discovered a large pericardial effusion causing tamponade. An emergency pericardiocentesis drained frank pus. Treatment with intravenous antibiotics, frequent pericardial drainage and a pericardectomy led to an excellent outcome, and a full recovery.