Our purpose was to produce a platelet substitute that could enhance haemostatic ability using rabbits with severe thrombocytopenia. We have developed polymerized albumin particles (polyAlb) for treatment of bleeding and focused on a dodecapeptide, HHLGGAKQAGDV (H12), as a useful ligand for activated platelet. This sequence occurs only at the carboxy-terminus of the fibrinogen gamma-chain (gamma 400-411). H12 was conjugated to the surface of polyAlb modified with poly(ethylene glycol) (PEG) chains to produce blood-compatible particles (H12-PEG-polyAlb) that had prolonged blood residence time and enhanced stability in vitro and in vivo. The H12-PEG-polyAlb was administered intravenously to rabbits with severe thrombocytopenia, and the ear bleeding time was measured in order to evaluate the haemostatic effect. The H12-PEG-polyAlb significantly shortened the ear bleeding time of severely thrombocytopenic rabbits and showed no effect on the inhibition or promotion of endogenous and exogenous coagulation activities. Furthermore, we could assess the haemostatic capacity of the H12-PEG-polyAlb, based on the relationship between transfused platelet count and the bleeding time. The H12-PEG-polyAlb may be a suitable candidate for an alternative to human platelet concentrates infused to treat bleeding in patients with severe thrombocytopenia.