Background: Initial fluid therapy is the cornerstone of hemodynamic resuscitation in pediatric patients suffering from septic shock. This study aimed to evaluate the association between fluid therapy during the first 12 hours from septic shock onset and clinical outcomes in a pediatric cohort.Method: This was a retrospective, observational study of consecutive pediatric patients with septic shock admitted to our multidisciplinary pediatric intensive care unit (PICU) between January 2012 and December 2019. Total fluid administration within the first 12 hours from septic shock onset, patient characteristics, and outcome measurements were collected from validated electronic medical records. Results: A total of 144 cases were included with an overall 28-day mortality rate of 20.1%. Among the survivors, the proportion of fluid received within the first 3 hours (36.9 % vs 25.4%, p=.004) and within the last 3 hours (18.9 % vs 21.3 %, p=.031) of the total amount administered over a 12 hour period from septic shock onset showed a significant difference compared with the non-survivors. The mortality rate was lower in the group receiving the highest proportion of the total administered fluid within the first 3 hours (13.9 % vs 26.4 %, p=.048). Patients receiving the highest proportion of fluid in the last 3 hours had a significantly higher mortality rate (29.6 % vs 14.4 %, p=.025). By multivariable logistic regression analysis, we also found that a higher proportion of administered fluid within the first and last 3 hours was associated with decreased mortality (OR, 0.951; 95% CI, 0.918-0.986; p=.028) and increased mortality (OR, 2.761; 95% CI, 1.175-6.495; p=.020), respectively.Conclusions: An increased fluid intake within the first 3 hours of septic shock onset is associated with a decreased 28-day mortality. Moreover, a higher administration of fluids from 9 to 12 hours after this onset seems to be related to a poorer survival outcome. Treating pediatric septic shock cases with higher amounts of fluid within the first 3 hours of onset and then with more conservative levels thereafter may lead to better survival outcomes.