A heparin-conjugated biodegradable polymer (PLA-heparin) by the direct coupling of heparin to polylactide (PLA) was synthesized and characterized. The surface exposed heparin content associated PLA-heparin was measured to be 0.067 microg/cm2. PLA-heparin coated surface has shown higher hydrophilicity rather than control PLA surface. The clotting time of PLA-heparin conjugate measured by activated partial thromboplastin time (APTT) was significantly prolonged as compared to PLA. The bioactivity of bound heparin measured by APTT corresponds to 17.4% of free heparin. It has been also demonstrated that the conjugation of heparin suppresses the protein adsorption as well as the platelet adhesion. These results indicate that the unique property of bound heparin has an inhibiting influence on the coagulation, plasma protein adsorption, and subsequent platelet adhesion systems. This novel PLA-heparin conjugate could be applied as blood/tissue compatible biodegradable materials for implantable medical devices and tissue engineering.