Human Domain Antibodies (dAbs) that bind to and inhibit the function of platelet glycoprotein VI (GPVI) have been isolated from phage display libraries and their efficacy demonstrated using in vitro models of platelet activation. Here we describe the properties of one such antibody, BLO8-1, which has been shown to specifically inhibit the binding of recombinant human GPVI to cross-linked collagen related peptide (CRP-XL) in vitro. BLO8-1 specifically binds to the platelet cell surface and prevents CRP-XL induced platelet aggregation in platelet-rich plasma, as well as inhibiting thrombus formation in whole blood under arterial shear conditions. Using a series of mutant GPVI molecules, BLO8-1 was shown to recognize an epitope within the collagen binding domain of GPVI, therefore the anti-thrombotic effect of this dAb is predicted to be due to direct blocking of the collagen-GPVI interaction. These data, together with the desirable properties of Domain Antibodies, show that dAbs could potentially be used to generate novel biopharmaceuticals with anti-thrombotic properties.