Purpose: We investigated the characteristics of Acinetobacter baumannii infection in critically ill patients with hematologic malignancies. Materials and Methods: The prospectively collected data of patients with hematologic malignancies admitted to a medical intensive care unit of a university hospital from 2007 through 2010 were reviewed retrospectively. Results: One hundred twenty-eight patients were included in the study, among whom 35 (27%) developed 39 A baumannii infections. Pneumonia was the most common infection site of A baumannii. Presence of neutropenia, underlying hematologic malignancy, and the disease status did not affect the acquisition of the infection. Advancing age, prior exposure to aminoglycosides, central venous catheterization, and presence of nasogastric tube were the independent risk factors for the development of A baumannii infections. The mortality rate was higher in patients with A baumannii infections compared with the ones without (P = .009). However, in multivariate analysis, low Glasgow coma scale, prior immunosuppressive treatment, neutropenia, invasive mechanical ventilation, and severe sepsis were independently associated with mortality, whereas presence of A baumannii infection was not. Conclusions: Despite the high mortality rate in critically ill patients with hematologic malignancies, presence of A baumannii infection was not an independent risk factor for mortality. © 2011 Elsevier Inc.