Purpose: The aim of this study was to assess the role of ABO blood groups in predicting disease severity and bleeding potential in children with Crimean-Congo hemorrhagic fever (CCHF). Methods: One hundred fifty-one hospitalized patients with CCHF were enrolled in this retrospective study. The patients were divided according to O- and non-O-(A, B and AB) blood groups (n=91 and n=60, respectively). They were also classified into two groups (severe and non-severe) based on disease severity (n=29 and n=122, respectively). Demographic characteristics, clinical findings, and hematologic and biochemical parameters of all patients were recorded on admission and discharge. Results: Although, in all cases, compared to the non-O blood group, the ratio of the blood group O was considerably higher (60% vs. 40%) and similarly so in severe cases (58.6% vs. 41.4%), this difference was not statistically significant (p>0.05). The aPTT at discharge and fever duration of the O-blood group were significantly higher than those of the non-O-blood group (p=0.042, p=0.034, respectively). The factor VIII level of the O-blood group was significantly lower than that of the non-O-blood group (p=0.040). Although the ratios of bleeding and severity were higher in the O-blood group compared to the other group, statistical significance was not reached (p>0.05). Conclusions: Consideration of the ABO blood group is important during diagnostic follow-up to assess the severity of CCHF. In clinical practice, pediatric CCHF patients with the O blood group need to be followed closely for tendency to bleed.