Background: Fluid administration can be lifesaving as fluid accumulation after initial resuscitation and stabilization of hemodynamics can lead to avoidable adverse effects and less favorable outcomes. Objective: The aim of the work was to evaluate whether even fluid balance in comparison to negative or even fluid status is correlated with increased morbidity and mortality rates in critically ill patients. Patients and Methods: An observational prospective study was done on 145 patients older than eighteen years, admitted to the general intensive care (Medical & Surgical ICU) units in Helwan University Hospitals and Ain Shams University Hospitals during the period from November 2020 till May 2021. Results: One hundred twenty-four patients (85.5%) who survived, having the median cumulative fluid balance of -110ml (IQR-2.1 – 2.2L) after four days following randomization while the median cumulative fluid balance of the 21 patients (14.5%) who didn't survive was 3800 ml (IQR 1.7-5.2L), after four days of ICU admission. Fluid balance more than 1.2 liters per day in our study had higher ICU complications: Increased risk of AKI, longer ICU and hospital stays, mechanical ventilation and fluid balance was an independent factor associated with increased mortality. Conclusion: It could be concluded that negative fluid balance for 4 days in critically ill patients was associated with less length of stay in the general ICU, and less mechanical ventilation duration, while positive fluid balance, leads to higher mechanical ventilation duration, vasopressors requirements, and significantly associated with higher mortality.