Intensive care unit delirium is a complex problem associated with significant negative consequences on patient outcomes. Delirium is also known as acute brain dysfunction, reflecting the evolving paradigm that it is a manifestation of acute organ dysfunction in the setting of neurotransmitter imbalances, inflammation, and metabolic derangements. In recent years, strides have been made towards better understanding its management, although much work remains to be done. Here we review the current state of knowledge regarding diagnosis, pathophysiology, risk factors, prevention, and management as supported by recent literature and the 2013 clinical practice guidelines on pain, agitation, and delirium.