Delirium is an acute and common problem often affecting frail and older persons in the acute care hospital, but can develop in any setting. It is associated with serious complications but can also be treatable if diagnosed early and managed properly. Preventive measures should be implemented in high risk patients, such as those with malnutrition, polypharmacy, infections, previous delirium, or dementia. Despite precautions, delirium is unavoidable in some cases and clinicians should be familiar with the typical features and varied presentations of this condition. Diagnosing delirium can be based on the DSM criteria, though multiple useful screening tools exist. Since delirium is almost always triggered by an underlying condition, an aggressive search for the causative insult(s) is essential in order that a targeted intervention be started promptly. Although there is neither any medication approved by the FDA for the treatment of delirium nor any robust evidence supporting the benefit of medications, there is general consensus that drug intervention can be attempted when non-pharmacological interventions have failed.