The clinical outcomes of patients infected with a single clone of an multidrug-resistant (MDR) strain of Acinetobacter baumannii were investigated. A matched comparative cohort study was conducted in a tertiary hospital in Korea. Thirty patients infected with single clone of MDR A. baumannii admitted to two intensive care units (ICUs) were matched to 30 control patients without A. baumannii, while controlling for concomitant diseases and severity of illness. All analyzed MDR A. baumannii isolates were identified as sequence type (ST) 92. In-hospital and in-ICU mortality rates did not differ significantly between the cases and controls (p=0.795 vs. p=0.796). Multivariate analysis demonstrated that MDR A. baumannii ST92 infection was the independent risk factor for prolonged hospital stay (odds ratio [OR] 13.12, 95% confidence interval [CI] 3.06-56.19, p=0.001), prolonged ICU stay (OR 9.66, 95% CI 2.73-34.13, p<0.001), and prolonged mechanical ventilation (OR 8.63, 95% CI 2.21-33.68, p=0.002). These findings indicate that MDR A. baumannii ST92 infection results in adverse outcomes of patients, and strict adherence to infection controls in ICUs should be encouraged.