The Effects of a compatibilizer, namely, an acrylonitrile-butadiene-styrene copolymer (ABS) grafted with maleic anhydrade (MAH) (ABS-g-MAH), on the mechanical properties and morphology of an ABS/polycarbonate (PC) alloy were studied The results showed that: a small quantity of ABS-g-MAH has a very good influence on the notched Izod impact strength of the ABS/PC alloy without compromising other properties such as the tensile strength, flexural strength, and Vicat softening temperature (VST). The impact strength of the ABS/PC alloy, to a great extent, depends on the loading of ABS-g-MAH and the degree of grafting (DG) of MAH in the ABS-g-MAH. DSC analysis and SEM observation confirmed that ABS-g-MAH could significantly improve the compatibility of the ABS/PC alloy.