Coronaviruses are important pathogens in humans that can cause diseases ranging from the common cold to more severe and even fatal respiratory illness, Studies have emphasized that patients diagnosed with COVID‐19 are susceptible to hyper-coagulation and thrombotic events, the symptoms range from mild disorders of coagulation indicators to disseminated intravascular coagulation (DIC).

Objective: Aim of the work in this study, was to investigate the effect of COVID‐19 disease on coagulation cascade of COVID‐19 infected patients, and to analyze the coagulation parameters of patients with COVID-19 pneumonia admitted to Sohag university hospital.

Patients and Methods: This study was conducted on forty COVID‐19 patients diagnosed by PCR, the patients were classified into 3 subgroups according to the severity of pneumonia mild, moderate and critical groups, compared with 20 persons of healthy control group.

Results: The results of the current study illustrated that the absolute lymphocyte was significantly lower in moderate and critical groups comparing to healthy control group, prothrombin concentration was significantly lower in moderate group comparing to healthy control group, concerning d-dimer and von Willbrand factor antigen vWF:Ag demonstrated significant elevations moderate and critical group comparing to healthy control group. Regarding protein C and Anti-Thrombin show lower level in moderate and critical groups comparing to healthy control groups.