Aim: Late-onset sepsis (LOS) in preterm infants can progress rapidly from minimal clinical signs and symptoms to septic shock which is associated with high mortality. The aim of this study was to describe the progression from sepsis to septic shock and evaluate our management performance with emphasis on time to treatments. Methods: This was a retrospective observational study including preterm infants ≤32 weeks gestation with LOS and septic shock defined as the requirement of fluids and vasopressors. Physiological changes and time to first diagnostics and treatments were determined from the point of first appearance of clinical signs and symptoms of sepsis (T ONSET ). Results: During the 10-year observational period, 279 infants developed LOS and 25 (8.9%) progressed to septic shock. The median (interquartile range) time from T ONSET to blood culture, administering antibiotics, fluid bolus and vasopressors was 8.4 (4.8-12.2), 9.2 (5.6-12.4), 14.6 (9.5-34.5) and 22.0 (14.6-44.7) h, respectively. Hypotension and raised lactate were prominent physiological changes in the progression to septic shock. Fluid bolus and vasopressors were administered when blood pressure was 20 and 41% below to what was normal before the infant became unwell. Vasopressors significantly increased blood pressure and heart rate. Mortality rate was 40% with no difference in time to treatments between survivors and non-survivors. Conclusion: Clinical recognition of the onset of sepsis in preterm infants remains difficult and contributes to delay of treatment. Once recognised, early administration of antibiotics, fluid bolus and vasopressors should be prioritised.