OBJECTIVE: To determine the costs associated with delirium in critically ill children. DESIGN: Prospective observational study. SETTING: An urban, academic, tertiary-care PICU in New York city. PATIENTS: Four-hundred and sixty-four consecutive PICU admissions between September 2, 2014, and December 12, 2014. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: All children were assessed for delirium daily throughout their PICU stay. Hospital costs were analyzed using cost-to-charge ratios, in 2014 dollars. Median total PICU costs were higher in patients with delirium than in patients who were never delirious ($18,832 vs $4,803; p 3 d with delirium; p