Delirium is a serious neuropsychiatric condition characterized by an acute change in cognition and attention that affects a significant proportion of hospitalized older adults and is associated with significant morbidity and mortality. Prevention of delirium is an important part of the care of hospitalized older adults. The Hospital Elder Life Program is a multicomponent intervention that has been shown to reduce the incidence of delirium. As many cases of delirium are overlooked, its diagnosis is important and can be achieved using the Confusion Assessment Method, which relies on four cardinal features of delirium: acute onset, inattention, altered level of consciousness, and disorganized thinking. The etiology of delirium is often multifactorial with contributions from predisposing factors (such as sensory impairment, chronic illness, and cognitive impairment) and precipitating factors (such as infection, polypharmacy, or illness). Once diagnosed, delirium should be evaluated with a thorough history, complete physical, medication review, and targeted tests in an effort to identify these factors.