The present invention relates to a single chain variable fragment (scFv 9O12.2) directed against human glycoprotein VI, constituted of the VH and VL domains of 9 O12.2.2 monoclonal antibody linked via a (Gly4Ser)3 peptide and followed by a “c-myc” flag, represented by SEQ ID NO:1. The invention also concerns functional variants of said scFv 9O12.2 fragment with identical heavy and light chains complementary determining regions 1, 2 and 3, and preferably humanized functional variants such as the humanized scFv fragments represented by SEQ ID NO:28 or SEQ ID NO:47. The invention also relates to nucleic acids encoding such a scFv fragment, expression vectors and host cells to produce such a scFv fragment, as well as therapeutic uses of such a scFv fragment.