Septic shock substantially alters the pharmacokinetic properties of ß-lactams with a subsequently high risk of insufficiently low serum concentrations and treatment failure. Considering their pharmacokinetic (PK)/pharmacodynamic (PD) index, prolonged infusions (PI) of ß-lactams extend the time that the unbound fraction of the drug remains above the minimal inhibitory concentration MIC (ft >MIC) and may improve patient survival. The present study is a monocentric, retrospective before-and-after analysis of septic shock patients treated with ß-lactams. Patients of the years 2015-2017 received intermittent bolus application whereas patients of 2017-2020 received PI of ß-lactams. The primary outcome was mortality at day 30 and 90 after diagnosis of septic shock. Mortality rates in the PI group were significantly lower on day 30 (PI: 41%, n=119/290 vs. IB: 54.8%, n=68/114; p=0.0097) and day 90 (PI: 47.9%, n=139/290 vs. IB: 62.9%, n=78/124; p=0.005). After propensity-score matching, 30- and 90-day mortality remained lower for the PI group (-10%). PI further reduced duration of invasive ventilation. PI of β-lactam antibiotics led to a stronger decrease in SOFA scores within a 14d-observation period. PI of ß-lactams significantly reduces mortality in patients with septic shock and may have beneficial effects on invasive ventilation and recovery from sepsis-related organ failure.