Background: Early diagnosis of sepsis is challenging as sepsis is a life-threatening organ dysfunction. The aim of the study was to investigate the role of both the presepsin and the blood culture in diagnosing of sepsis in ICU patients. Methods: A case control study was conducted in clinical pathology department and ICU, faculty of Medicine in zagazig university hospital, Egypt from May 2021 to December 2021.We included 46 patients; they were classified into septic and non-septic group. The septic group included patients with suspected or documented infection in the ICU with at least two or more of the following criteria; leucocytes >12,000/mm3 or < 4000/mm3, temperature > 38°c or < 36°c, heart rate>90bpm or respiratory rate>20 breaths/min. The exclusion criteria included pregnancy or end stage liver disease. The non-septic group included those with negative septic criteria admitted to the ICU. Blood sample were collected within the first 6 hours of ICU admission from all patients to estimate the presepsin, CRP and blood culture. Results: Blood culture for the septic group was positive in 58% and the most common organism was Klebsiella pneumonia (19%). Out of the 31 patients included in the septic group. Regarding presepsin, there were 58% of the septic group had high presepsin more than 65.8 pg/ml (cut off value); it was elevated in 61% of the patients with culture-positive results and about 55% with negative blood culture results. Comparing septic and non-septic groups regarding septic biomarkers; there was a statistically significant difference with CRP and Presepsin. There was no statistically significant difference on comparing the survival rate among the septic group regarding septic markers. 62% of the non-survivors had an elevated presepsin. Also, 86% of the non-survivors had a positive blood culture. There was no significant correlation between the presepsin and the results of the blood culture. Conclusion: Presepsin is not the definitive test for diagnosis of sepsis. However, can be used as a mark for gram negative bacteria