The invention relates to isolated single-domain antibodies (sdAb) directed against von Willebrand Factor (VWF) D′D3 domain and chimeric polypeptides comprising thereof such as blood clotting factors and their uses in therapy such as in the prevention and treatment of hemostatic disorders. The invention also rotates to a method of extending or increasing half-life of a therapeutic polypeptide comprising a step of adding to the polypeptide sequence of said therapeutic polypeptide at least one sdAb directed against VWF D′D3 domain.