Delirium is a transient condition characterized by sudden and fluctuating disturbances in cognitive function. The condition can be considered a sign of the brain's vulnerability and diminished resilience to insult. Among the many clinical manifestations are cognitive, psychomotor, and sleep disturbances. Delirium is associated with longer hospital stays, worse functional outcomes, and higher mortality. Although up to 48% of patients who have had a stroke develop delirium, the condition has been studied much less in these patients than in general medicine, surgical, and intensive care patients. Coexisting neurologic deficits in patients with stroke limit the use of screening tools that are widely accepted in other populations. The variability of reported assessment methods highlights the need for delirium screening guidelines in stroke. Further, risk factors that are specific to stroke may play an important role in the etiology of delirium, along with such well-known factors as older age and infections. The delirium literature lacks data on differences in clinical manifestations and course in the various types of stroke. Here we review predisposing factors, diagnostic methods, and biomarkers of delirium in stroke and discuss aspects that need further research.