This study aims to investigate the extended leukocyte parameters, known as cell population data (CPD), in Crimean-Congo hemorrhagic fever (CCHF) and to evaluate their diagnostic performance in assessing mortality risk and intensive care unit (ICU) admission requirements. The study included a total of 260 participants, comprising 200 individuals diagnosed with CCHF and 60 healthy controls. CPD analyses were conducted using a Sysmex-XN 9000 complete blood count analyzer. Elevated levels of immature granulocyte (IG) percentage, neutrophil reactivity indices (Ne-X, Ne-Y), dispersion of neutrophil NE-SSC and NE-SFL signals (Ne-WX, Ne-WY), monocyte metabolic activity (Mo-X), and lymphocyte metabolic activity (Ly-X) were observed in CCHF patients compared to controls. Conversely, lymphocyte metabolic activity (Ly-Y) and monocyte fluorescence intensity (Mo-WY) were lower in patients than in controls. In discriminating mortality, IG#, IG%, Ne-WY, and Ly-Y exhibited higher AUC values than other CPDs. Additionally, for predicting ICU requirements, IG#, IG%, and Ne-WY demonstrated higher AUC values compared to other CPDs. IG, Ne-WY, and Ly-Y have the potential to serve as biomarkers for predicting mortality in CCHF. Furthermore, IG and Ne-WY may emerge as innovative and reliable biomarkers for identifying severe cases and predicting the need for ICU admission.