Anemia and elevated red cell distribution width (RDW) or mean corpuscular volume (MCV) are associated with an adverse prognosis in patients with cardiovascular disease and critical illness. Limited data exist regarding these associations in unselected cardiac intensive care unit (CICU) patients.Retrospective cohort study of CICU patients between January 1, 2007, and December 31, 2015, with a hemoglobin (Hb) level measured at admission. Multivariable regression was performed to determine predictors of hospital mortality, and Kaplan-Meier analysis was used to determine post-discharge survival.We included 9644 patients with a mean age of 67.5 ± 15.1 years, including 3604 (37.4%) females. The median (IQR) values of Hb, MCV and RDW were 12.2 g/dL (10.6, 13.7), 90.7 fL (87.3, 94.2) fL, and 14.1% (13.3, 15.8), respectively. Anemia (admission Hb < 12 g/dL) was present in 4434 (46%) patients. A total of 845 (8.8%) patients died in the hospital. Patients with anemia had higher hospital mortality (11.3% vs. 6.6%, unadjusted OR 1.82, 95% CI 1.58-2.10, p < 0.001). After multivariable regression, admission Hb and MCV were not significantly associated with hospital mortality (both p > 0.1), while admission RDW (adjusted OR 1.12 per 1%, 95% CI 1.07-1.18, p < 0.001) was significantly associated with hospital mortality. Hospital survivors with lower Hb, higher MCV, or higher RDW had lower post-discharge survival.Elevated RDW on admission was independently associated with higher hospital mortality in CICU patients. These data emphasize the importance of hematologic abnormalities for mortality risk stratification in CICU populations.