Pseudomonas aeruginosa bacteremia is associated with high morbidity and mortality in critically ill patients. In this study, we assessed risk factors for clinical failure of first definitive therapy for P. aeruginosa bacteremia in critically ill patients. All patients with P. aeruginosa bacteremia who entered the intensive care unit in Gifu University Hospital from January 2006 to December 2015 were retrospectively identified from electronic records. Risk factors associated with clinical failure of the first definitive therapy for P. aeruginosa bacteremia were analyzed by logistic regression analysis. A total of 28 patients were enrolled in the analysis. On multivariate analysis, severe burns (odds ratio [OR] = 70.9, 95% CI 2.9-1720.3; p = 0.009) and SOFA score ≥ 10 (OR = 28.5, 95% CI 1.1-754.3; p = 0.045) were significant factors in the clinical failure of first definitive therapy for P. aeruginosa bacteremia. The clinical success rate of first definitive therapy was significantly reduced in patients with these risk factors compared with those without them (p < 0.001). Severe burns and a SOFA score (≥ 10) were significant risk factors associated with the clinical failure of first definitive therapy for P. aeruginosa bacteremia in critically ill patients. We therefore recommend the use of therapeutic drug monitoring to optimize antibiotic dosing in these critically ill patients.