Background: In this study, we aimed to investigate the diagnostic and prognostic utilities of presepsin and procalcitonin (PCT) in critically ill patients with suspected sepsis, for whom sepsis was diagnosed clinically based on the Survival Sepsis Campaign (SSC) criteria and to compare it with recent criteria of Sepsis-3. Methods: Blood samples for biomarker measurements of presepsin and PCT were drawn on days 1, 3 and 7 of ICU admission in a total of 26 patients. All patients were followed-up until death or discharge. All studied biomarkers were analyzed according to the diagnosis and severity of sepsis and for prognosis (all-cause mortality) at days 1, 3 and 7. Agreement between the diagnosis of clinical sepsis and presepsin or PCT-based sepsis was assessed using Cohen’s kappa Results: Clinical sepsis (based on Sepsis-3) and presepsin or PCT-based sepsis showed poor agreement (Kappa<0.4). Presepsin levels at day1 correlated significantly with mortality (r=0.45, P; 0.02). The diagnostic value of both presepsin and PCT to diagnose sepsis was weak (Area under curve (AUC) <0.75). The overall agreement in sepsis diagnosis was fair to good based on the both clinical criteria (P<0.05, Kappa: 0.5-0.75). More than 80% of patients (N=21) had sepsis based on presepsin upon admission. Both clinical criteria predicated that less than 20% of patients (N=5) had sepsis upon admission. Conclusion: Based on our findings, the overall agreement between the diagnosis of clinical sepsis and presepsin or PCT-based sepsis was poor. Also, our results show that the new Sepsis-3 definitions were accurate and equal to the previous definition of SSC guideline. Although, availability of diagnostic assays is variable in Iran, but, it seems that addition of developing decision tools that utilize biomarkers to help aid the rapid diagnosis of sepsis is necessary and may  improve patient outcomes. Keywords: Presepsin, Pro Calcitonin, Sepsis, Diagnosis