Acinetobacter baumannii is an important pathogen in hospitalized patients, particularly those in the intensive care unit (ICU). A total of 21 A. baumannii (6 from 5 patients and 15 from environmental samples) were isolated in the ICU and the isolation room of a state hospital in June 2011. The possible source of the outbreak was investigated. A. baumannii isolates were identified using conventional biochemical tests, BBL Crystal Identification Systems, OXA-51 specific PCR, and 16S rDNA sequencing. All the isolates were multidrug-resistant, showing resistance to cephalosporins, carbapenems, fluoroquinolones, and the aminoglycoside group of antibiotics. Pulsed-field gel electrophoresis suggested that all A. baumannii isolates were derived from a common source.