Polylactide (PLA) is biodegradable and has been useful in various biomedical applications. Since the majority of the biodegradable polymers in clinical use are rather stiff materials that exhibit limited extendibility with low elongation at break values, the physical and mechanical properties of PLA must be improved to allow for more biomedical applications. Poly(ester-urethane) structure polymer materials were prepared; PLA was reacted with a small amount of trimethyl hexamethylene diisocyanate to obtain ductile PLA with markedly improved mechanical properties. Elongation at break was increased by more than 20 times while maintaining relatively high tensile stress when compared to pristine PLA. Impact resistance (notched) improved 1.6 times. Thus, the modified PLA biodegradable polymers presented here may have greater application as a biomedical material due to its enhanced mechanical properties.