Background: sepsis refers to the presence of a serious infection that correlates with systemic and uncontrolled immune activation. Few studies had analyzed eosinophil count as a prognostic marker of outcome in patients with infection. Eosinopenia is an interesting biomarker because the eosinophil count is always measured in clinical practice and the additional costs would therefore be negligible.The aim of this wrk: this studyaimed to test the value of eosinopenia in the diagnosis of sepsis in critically ill patients admitted to ICUs. Patients and Methods: this prospective observational, randomized study was conducted on 50 adult critically ill patients who were admitted to ICU of Ahmed Maher Teaching Hospitalin the period from March 2017to July 2017. They either had sepsis on admission or not. An informed written consent was obtained from patients and/or relatives before starting this study. Inclusion criteria were patients more than 18 years old and less than 60 years that were critically ill either in sepsis or not. Exclusion criteria were patients less than 18 years old and more than 60 years old, patient or relatives who refused to be included in this study, those with hematological cancer, HIV infection, bronchial asthma and other atopic disorders like hay fever, atopic dermatitis and allergic conjunctivitis and increased levels of eosinophil count as part of any parasitic infection or trauma patients. Results: comparison between infected and non-infected studied patients was statistically significant as regard variables of SOFA score, APACHE II score at admission, TLC and Eosinophil count at admission (p-value˂0.05). There were no statistical significant differences as regard length of ICU stay (p˃0.05). Multivariate regression analysis showed statistically significant differences and was independent predictors for infection as follow: total leucocytic count, eosinophil count at admission and SOFA score. The AUC for eosinophil count to predict was 95% with optimal cut off value was 50 cells/mm3 with a sensitivity of 92.85% and specificity of 93.33% with P value <0.001.Conclusion: the result of the present study revealed that eosinophil counts was ˂50 cells/mm3 at admission time to ICU was a predictor for diagnosis of sepsis in critically ill patients. However, eosinophil counts at admission time to ICU were not a specific indicator of mortality. Recommendations: eosinophil counts are cheap and easily accessible test can be used to guide for sepsis diagnosis and treatment.Larger studies are needed to determine the prognostic value of this test and establish better cutoff values.