Delirium is an acute and fluctuating disorder characterized by a disturbance in attention and cognition. Delirium is underdiagnosed by clinicians, but there are excellent diagnostic tools using history and physical examination that can assist clinicians in making the diagnosis in multiple settings (ie, CAM, CAM-ICU, 3D-CAM, bCAM, 4AT, and UB-CAM). Delirium is caused by underlying medical conditions and is often multifactorial, so a full diagnosis requires a careful assessment for a wide range of underlying conditions. Physical examination has not been well studied in this regard, but still can provide useful clues to the clinician.