Oxidation of fibrinogen with hypochlorite inhibited the fibrin network self-assembly even at the lowest concentration of the oxidant. The analysis of the results of protein electrophoresis at this hypochlorite concentration showed the absence of fragmentation of the protein and covalent cross-linking of its chains. The study of the areas responsible for the conversion of fibrinogen into fibrin by mass spectrometry showed that they are not subject to oxidative damage. However, we identified oxidized amino acid residues, which could affect the protofibril aggregation.