The aim of this study was to improve the toughness of UPE resin by using an aromatic hyperbranched polyester. The aromatic hyperbranched polyester(HBP) was synthesized and the end-group of the polymer was modified to methacrylate-terminated hyperbranched polyester. (MA-HBP) We characterized HBP and the resulting MA-HBP using 1H-NMR and DSC. MA-HBP, up to 5 phr, was blended with UPE, The glass transition temperature was not affected by the addition of MA-HBP, but the thermal stabilities of UPE blended with MA-HBP increased. It was found that the fracture toughness of UPE blended with MA-HBP increased by about 25%, as MA-HBP was added up to 3 phr. It slightly decreased with the further addition of MA-HBP to 5 phr.