BACKGROUND: Delirium is common in the medical and surgical intensive care unit (ICU), and its association with morbidity and mortality is well described. Despite emerging data, which have highlighted a growing critical care burden in the contemporary cardiac ICU (CICU), much less is known about delirium in this specialized setting. METHODS AND RESULTS: Records for consecutive CICU patients aged ≥18 years who were admitted to our academic, tertiary care institution from December 2012 to March 2014 for a primary cardiovascular diagnosis were reviewed. Only those with a documented Confusion Assessment Method for ICU score were included in the final analysis. Baseline characteristics, resource use, and outcomes were collected. Disease severity was assessed using the modified Acute Physiology and Chronic Health Evaluation II score and the Simplified Acute Physiology ScoreII. Multivariable logistic and linear regression models were constructed to evaluate the association between CICU delirium, length of stay, and death. Among 590 patients included, the prevalence of CICU delirium was 20.3%. Delirious patients were older, had greater disease severity, required longer ICU stays (5 vs 2 days; P < .001), and had higher mortality (27% vs 3%; P < .001). In the adjusted setting, delirium remained strongly associated with both increased mortality (P < .001) and length of stay (P = .001). CONCLUSIONS: In those with cardiac critical illness, delirium is common and associated with worse survival and greater resource consumption. Future study is needed to validate these findings and to develop effective strategies for the early identification and treatment of the delirious CICU patient.