Fluid infusion represents one of the cornerstones of resuscitation therapies in order to increase oxygen delivery during septic shock. Fluid overload as a consequence of excessive fluid administration seems to be linked to worse long-term outcome. However, its immediate effect on patient's clinical state is poorly described. The goal of this study was to assess the impact of FO on SOFA score kinetics as a surrogate marker of organ dysfunction from day 0 to day 5. Retrospective, multicenter, investigator-initiated study. All adult patients (> 18 years old) admitted from January 2012 to April 2017 in one of the three ICUs for septic shock, secondary to peritonitis or pulmonary infection and mechanically ventilated, were included. Univariate analysis was performed with Student's and chi-square test, for continuous and categorical variables, respectively. A multivariate linear regression model evaluated the impact of FO on delta SOFA score from day 0 to day 5. Secondly, a multivariate mixed-model accounting for repeated measures analyzed the impact of FO on SOFA score kinetics. One hundred twenty-nine patients met the inclusion criteria and were assigned into FO and no FO groups. FO occurred in 39% of the patients. The difference between SOFA score at day 0 and day 5 was more than twofold higher in the no FO group than in the FO group with a difference of 2.37 between the two groups (4.52 vs. 2.15;  = 0.001). Cumulative fluid intake at day 5 was higher in the FO group (2738 vs. 8715 ml,  < 0.001). In multivariate analysis, FO was associated with delta SOFA score: aRR = 0.15 (95% CI 0.03-0.63;  = 0.009). In mixed model, the regression coefficient for fluid overload status (  = 1.16;  = 0.014) indicated that the slope for SOFA score kinetic was less pronounced for patients with FO than for patients without FO. FO patients had a more prolonged multi-organ failure according to SOFA score kinetics during septic shock from resuscitation phase to day 5.