Delirium occurs frequently in the critically ill child. It is a syndrome characterized by an acute onset and fluctuating course, with behaviors that reflect a disturbance in awareness and cognition. Delirium represents global cerebral dysfunction due to the direct physiologic effects of an underlying medical illness or its treatment. Pediatric delirium is strongly associated with poor outcomes, including increased mortality, prolonged intensive care unit length of stay, longer time on mechanical ventilation, and increased cost of care. With heightened awareness, the pediatric intensivist can detect, treat, and prevent delirium in at-risk children.