Background: Sepsis can result in systemic multi-organ dysfunction and is brought on by an unbalanced host response to infection. TSH, T4 and T3 levels are decreased as a result of the changes in thyroid hormones. This hormonal confluence has been referred to as "Euthyroid Sick Syndrome (ESS)" or "Non-Thyroid Illness Syndrome" since it does not signify intrinsic thyroid dysfunction. Objective: To determine whether there is a connection between serum T3 levels and sepsis outcomes, particularly mortality in patients hospitalised to the PICU of Benha University Hospitals. Patients and methods: This study was prospective cohort study. We studied 100 children aged 1 month-18 years who were diagnosed with sepsis. For each patient, age, gender, mortality and outcome were noted. Study sample included 100 patients were collected from the pediatric intensive care unit at Pediatric Department, Benha University Hospitals over 6 months. All patients had serum free T3 levels measured, and all data were collected at the time of diagnosis. Patients were then followed until discharge or death, and they were separated into two groups based on outcome: the died (70 patients) and survived (30 patients) groups. Results: Serum T3 level was low in 93% of septic patients who died, while only 25 % did in the survived group. So, low T3 levels are associated with increased mortality in the paediatric critical care unit. Further investigation found that serum T3 levels of ≤ 1ng/dL had a significant relationship with mortality. Conclusion: Our study found that serum T3 level was low in 93% of septic patients who died, while only 25 % did in the survived group. So, low T3 levels had significant relationship with mortality in PICU.