Septic shock (SS) is associated with high morbidity and mortality rate. Early antibiotic therapy administration in septic patients was shown to reduce mortality but its impact on mortality in a prehospital setting is still under debate. To clarify this point, we performed a retrospective analysis on patients with septic shock who received antibiotics in a prehospital setting.: From April 15, 2017 to March 1, 2020, patients with septic shock requiring Mobile Intensive Care Unit (MICU) intervention were retrospectively analyzed to assess the impact of prehospital antibiotic therapy administration on a 30-day mortality. Three-hundred-eight patients with septic shock requiring MICU intervention in the prehospital setting were analyzed. The mean age of the study population was 70 ± 15 years. Presumed origin of SS was mainly pulmonary (44%), digestive (21%) or urinary (19%) infection. Overall 30-day mortality was 29%. Ninety-eight (32%) patients received antibiotic therapy.Using Cox regression analysis, we showed that prehospital antibiotic therapy significantly reduces 30-day mortality for patients with septic shock (hazard ratio =0.56, 95%CI [0.35-0.89], p = 0.016). In this retrospective study, prehospital antibiotic therapy reduces 30-day mortality of septic shock patients cared by MICU. Further studies will be needed to confirm the beneficial effect of prehospital antibiotic therapy in association or not with prehospital hemodynamic optimization to improve the survival of septic shock patients.