Introduction: Coagulation dysfunction and thromboembolism emerge as strong comorbidity factors in severe COVID-19. However, it is unclear when particularly platelet activation markers and coagulation factors dysregulated during the pathogenesis of COVID-19. Here, we sought to assess the levels of coagulation and platelet activation markers at moderate and severe stages of COVID-19 to understand the pathogenesis. Methods: To understand this, hospitalized COVID-19 patients with (severe cases that required intensive care) or without pneumonia (moderate cases) were recruited. Phenotypic and molecular characterizations were performed employing basic coagulation tests including prothrombin time (PT), activated partial thromboplastin time (APTT), D-Dimer, and tissue factor pathway inhibitor (TFPI). The flow cytometry-based multiplex assays were performed to assess FXI, anti-thrombin, prothrombin, fibrinogen, FXIII, P-selectin, sCD40L, plasminogen, tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), and D-Dimer. Results: The investigations revealed induction of plasma P-selectin and CD40 ligand (sCD40L) in moderate COVID-19 cases, which were significantly abolished with the progression of COVID-19 severity. Moreover, a profound reduction in plasma tissue factor pathway inhibitor (TFPI) and FXIII were identified particularly in the severe COVID-19. Further analysis revealed fibrinogen induction in both moderate and severe patients. Interestingly, an elevated PAI-1 more prominently in moderate, and tPA particularly in severe COVID-19 cases were observed. Particularly, the levels of fibrinogen and tPA directly correlated with the severity of the disease. Conclusions: In summary, induction of soluble P-selectin, sCD40L, fibrinogen, and PAI-1 suggests the activation of platelets and coagulation system at the moderate stage before COVID-19 patients require intensive care. These findings would help in designing better thromboprophylaxis to limit the COVID-19 severity.Keywords: FXIII; coagulation; platelet activation; thromboembolism; tissue factor pathway inhibitor; tissue plasminogen activator.