Background: Bloodstream infections (BSI) are associated with increased morbidity and mortality, especially when caused by gram-negative or fungal pathogens. The objective of this study was to assess the impact of fast ID/AST with the Accelerate Pheno ™ system (AXDX) from May 2018 to December 2018 on antibiotic therapy and patient outcomes. Methods: A pre-post quasi-experimental study of 200 patients (100 pre-AXDX implementation and 100 post-AXDX implementation) was conducted. The primary endpoints measured were time to first antibiotic intervention, time to most targeted antibiotic therapy, and 14-day hospital mortality. Secondary endpoints included hospital and intensive care unit (ICU) length of stay (LOS), antibiotic intensity score at 96 hours, and 30-day readmission rates. Results: Of 100 patients with gram-negative bacteremia or candidemia in each cohort, 84 in the pre-implementation group and 89 in the AXDX group met all inclusion criteria. The AXDX group had a decreased time to first antibiotic intervention (26.3 vs 8.0 p=0.003), hours to most targeted therapy (14.4 vs 9, p=0.03), hospital LOS (6 vs 8, p=0.002), and average antibiotic intensity score at 96 hours (16 vs 12, p=0.002). Both groups had a comparable 14-day mortality (0% vs 3.6%, p = 0.11). Conclusion: In this analysis of patients with gram-negative bacteremia or candidemia, fast ID/AST implementation was associated with decreased hospital LOS, decreased use of broad-spectrum antibiotics, shortened time to targeted therapy, and an improved utilization of antibiotics within the first 96 hours of therapy.