With the aim to modify the brittleness of polylactic acid (PLA), it was firstly melt blended with thermoplastic polyurethane (TPU) at six different PLA wt % of 100, 90, 80, 70, 60, and 50 compositions. The properties of PLA/TPU composite were characterized by means of electron microscopy, rheological, mechanical and thermal methods. The results showed that the brittle fracture of pure PLA was gradually transformed into ductile fracture with the addition of the TPU elastomer. The notched impact strength of the composite at 10 wt % TPU was over three times higher than that of pure PLA. The composite was found to be a partially miscible system with shifted glass transition temperatures. The molten blend was shear-thinning fluid and it could be processed by conventional thermoplastic processes such as extrusion and injection molding. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 855-861, 2011