Delirium is an acute disturbance in attention, cognition, and awareness that fluctuates over time. Delirium is characterized by three subtypes: hyperactive, hypoactive, and mixed. It occurs in 11% to 25% of older adults in inpatient settings and is associated with a significant financial burden. Older age, multiple comorbidities, recent surgery, and polypharmacy are independent risk factors for delirium. The diagnosis is clinical but can be challenging due to overlapping symptoms with dementia and depression. The Confusion Assessment Method is a screening tool that is 94% to 100% sensitive and 90% to 95% specific for delirium. There is no evidence to support medication use for delirium prevention. Nonpharmacologic interventions, such as sufficient hydration and nutrition, early mobilization, infection control, and frequent orientation, can prevent and treat delirium. Physical restraints should be avoided, but if needed in patients at significant risk of injury to themselves or others, their use should be reassessed at least every 24 hours. No medications are approved by the U.S. Food and Drug Administration for the treatment of delirium. If pharmacologic therapy is indicated, second-generation antipsychotics such as olanzapine, risperidone, and quetiapine are preferred over haloperidol because of their faster onset of action and fewer adverse effects. Patients hospitalized with prolonged delirium have approximately three times the chance of dying in the following year compared with patients with a quick resolution of delirium or no symptoms; therefore, prevention and early detection should be emphasized.