BACKGROUND & OBJECTIVES: Crimean-Congo hemorrhagic fever (CCHF) is a fatal disease, caused by a tick-borne virus (Nairovirus), having a high mortality rate. The study was aimed to evaluate the risk factors, the presenting symptoms and findings of the patients with prediagnosis of CCHF disease, and to compare these variables between the CCHF-positive and CCHF-negative patients. It was also aimed to develop a scoring formula for the diagnosis of CCHF. METHODS: In total, 281 patients who were admitted to the Sabuncuoglu Serafeddin Training and Research Hospital, Amasya, Turkey between 2011 and 2015 and were prediagnosed with CCHF based on the clinical symptoms, laboratory findings and risk factors were included in the study. The definitive laboratory diagnosis of patients with prediagnosis of CCHF was ensured via molecular and serological methods. In addition, a mathematical diagnostic scoring formula was developed for enhancing the laboratory results of CCHF. RESULTS: The ratio of certain clinical symptoms such as fever (p<0.001), headache (p<0.001), widespread body pain (p<0.001), fatigue (p = 0.001), nausea and vomiting (p = 0.013) in CCHF-positive patients were found to be significantly higher compared to the ratio in CCHF-negative patients. In terms of laboratory findings such as presence of leucopenia (p<0.001), creatine kinase (CK) elevation (p<0.001), thrombocytopenia (p<0.001), aspartate aminotransferase/alanine aminotransferase (AST/ALT) elevation (p<0.001), lactate dehydrogenase (LDH) levels (p = 0.002), absence of abnormal findings on chest radiograph (p = 0.042), and the absence of anaemia (p = 0.007), the CCHF-positive patients had higher rates in comparison to CCHF-negative ones. INTERPRETATION & CONCLUSION: It was inferred that certain clinical symptoms and laboratory findings such as fever, headache, widespread body pain, fatigue, leucopenia, nausea, vomiting, high CK levels, thrombocytopenia, AST/ ALT elevation and elevated LDH levels are highly specific and are required to be considered in the definitive diagnosis of CCHF, particularly in regions where this infection is observed as endemic.