One of the key players in both hemostasis and thrombosis is von Willebrand factor (vWF), which demonstrates a duality between these two processes. Thrombus is structured by numerous elements, including endothelial cells, platelets, plasma proteins and shear stress alteration. In circulation, once a vessel wall is injured, collagen is exposed and platelets attach to the site of injury. Accordingly, vWF mediates adherence of platelets to the damaged vessel wall by binding both to the collagen and platelet receptor. A growing body of data also indicates a role for neutrophil extracellular traps (NETs) in human thrombosis as scaffolds for vWF, promoting thrombosis. VWF also mediates the protection of factor VIII, a main cofactor of the intrinsic clotting pathway. Since vWF plays a critical role in both thrombotic and bleeding events, a decreased plasma level of this factor may point to a bleeding disorder, while an elevated plasma level may predict occurrence of thrombosis. Since thrombotic events are the foremost cause of death, inhibiting the vWF activity would be a novel prophylaxis to reduce these events. Though, accumulated data have made vWF a promising focus for research on cardiovascular diseases (CVD). This chapter, however, aims to clarify the role of vWF in thrombus formation and pathogenesis of thrombosis.