Constrictive pericarditis can result from a stiff pericardium that prevents satisfactory diastolic filling. The distinction between constrictive pericarditis and other causes of heart failure, such as restrictive cardiomyopathy, is important because pericardiectomy can cure constrictive pericarditis. Diagnosis of constrictive pericarditis is based on characteristic haemodynamic and anatomical features determined using echocardiography, cardiac catheterization, cardiac MRI, and CT. The Mayo Clinic echocardiography and cardiac catheterization haemodynamic diagnostic criteria for constrictive pericarditis are based on the unique features of ventricular interdependence and dissociation of intrathoracic and intracardiac pressures seen when the pericardium is constricted. A complete pericardiectomy can restore satisfactory diastolic filling by removing the constrictive pericardium in patients with constrictive pericarditis. However, if inflammation of the pericardium is the predominant constrictive mechanism, anti-inflammatory therapy might alleviate this transient condition without a need for surgery. Early diagnosis of constrictive pericarditis is, therefore, of paramount clinical importance. An improved understanding of how constrictive pericarditis develops after an initiating event is critical to prevent this diastolic heart failure. In this Review, we discuss the aetiology, pathophysiology, and diagnosis of constrictive pericarditis, with a specific emphasis on how to differentiate this disease from conditions with similar clinical presentations.