Crimean-congo hemorrhagic fever (CCHF) is a viral disease that can be seen in people epidemically or as single patient. CCHF is a highly deadly disease caused by Nairovirus from Bunyaviridae family. Endothelial damage caused by secreted cytokines plays an important role in the pathophysiology of the disease. Reactive oxygen species (ROS) are highly cytotoxic. Intracellular and extracellular antioxidants are the mechanisms that protect the cell from the cytotoxic effects of the ROS. In this study, malondialdehite (MDA), superoxide dismutase (SOD), glutation peroxidase (GSHPx), glutation reductase (GR), catalase (CAT) enzyme activities and vitamin E - one of the antioxidant vitamins, values are examined to evaluate how oxidant/antioxidant value is affected in patients with CCHF. 47 patients diagnosed as CCHF with control group that is made of 41 healthy individuals that matched to patient group as sex and age contributed to study. All individuals' plasma SOD, CAT, GSHPx, GR, and vitamin E values and erythrocyte MDA levels were determined. SOD enzyme activity is increased (p<0.05) and CAT, GSHPx, GR enzyme activities did not change in CCHF patient (p>0.05). Vitamin E values turned out to be lower than control group (p<0.05). Plasma and erythrocyte MDA levels were higher than control group (p<0.05).