Crimean-Congo hemorrhagic fever (CCHF) is a life-threatening disease that develops as a result of infection by a member of the Nairovirus genus of the Bunyaviridae family, and its initial symptoms are not specific. In patients with severe clinical progression, in particular, the neutrophil rate is high, whereas lymphocyte and monocyte levels are low. A total of 149 patients, in whom the diagnosis was confirmed with reverse transcriptase PCR, were included in the study. In order to compare patient clinical progression severity, we divided the patients into two groups. For group 1, Çevik's severity score was used. The patients who had a platelet/lymphocyte ratio (PLR) <41 constituted group 2. Of 149 patients, 20 (13.4 %) were determined as group 1 (Çevik's classification) and 38 (25.5 %) were determined as group 2 (PLR <41). Of 11 deaths, 4 (36.4 %) patients were from group 1 and 7 (63.6 %) were from group 2. This is the first study to our knowledge to analyse the relationship between severity and PLR in patients with CCHF. PLR is a simple laboratory test that can aid in determining the prognosis of individuals with this disease.