Abstract Objectives The aim of this study was to determine the clinical characteristics of, antibiotic therapy for, and clinical outcome of Pseudomonas aeruginosa infection among bacteremic adults who visit the emergency department (ED). Methods Bacteremic adults who visited the ED were identified retrospectively from January 2007 to December 2007. Demographic characteristics, underlying illnesses, severity, bacteremic pathogens, antimicrobial agents, and outcome were determined from chart records. Results The records of 340 eligible bacteremic adults were analyzed; their mean age was 66.2 years, and major comorbidities included hypertension (175 patients, or 51.5%), diabetes mellitus (124, or 36.5%), and malignancy (87, or 25.6%). Among the 379 bacteremic isolates, Escherichia coli (139 isolates, or 6.6%) and Klebsiella pneumoniae (63, or 16.6%) were the major pathogens, whereas P aeruginosa (15, or 4.0%) was the third-leading gram-negative isolate. Of note, both 30-day mortality (33.3% vs 8.9%, P = .01) and the proportion of empirically inappropriate antibiotics (86.7% vs 31.4%, P < .001) were higher in bacteremia caused by P aeruginosa than in bacteremia not caused by P aeruginosa in univariate analysis. Moreover, multivariate analysis identified 3 independent factors related to P aeruginosa bacteremia: surgery during the 4 weeks before ED arrival (adjusted odds ratio [AOR], 12.7; 95% confidence interval [CI], 1.68-95.7; P = .01), malignancy (AOR, 4.57; 95% CI, 1.27-16.3; P = .02), and community onset (AOR, 0.14; 95% CI, 0.04-0.47; P = .002). Conclusions For bacteremic adults who visited the ED, P aeruginosa was associated with a high mortality rate and a high proportion of empirically inappropriate antibiotic therapy. Identification of clinical predictors of P aeruginosa bacteremia would improve the quality of care and the use of appropriate antibiotics in the ED.