Poly(butyleneadipate-co-terephthalate) (PBAT) was used to toughen poly(lactic acid) (PLA) with the addition of poly(methyl methacrylate)-poly (butyl acrylate)-poly(methyl methacrylate) (MAM) through melt blending. The impact toughness and tensile toughness of the PLA/PBAT/MAM ternary blends were greatly enhanced when the MAM content was higher than 5%.For PLA/PBAT/MAM (80/15/5) blend, the notched impact strength was as high as 42.4 kJ/m 2 , and the elongation at break reached 194.7%. The structure-property relationship of the PLA/PBAT/MAM ternary blends were studied through scanning electron microscopy, dynamic mechanical analysis, and contact angle measurements. It is found MAM and PBAT have a synergistic toughening effect on PLA, the MAM acts as not only a compatibilizer but also a toughening agent, which can improve the compatibility and enhance the interfacial adhesion between PLA and PBAT. As a result, the overall mechanical properties of PLA blends were improved significantly. This result provides a simple to operate and more efficient method for PLA toughening.