The blend composition at the surface of an injection-molded product for binary blends of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) is studied. As well known, low molecular weight fraction is segregated on the surface of an injection-molded plate with broad molecular weight distribution to minimize applied shear stress, which was confirmed also in our experiments using pure PC. In the case of the blend of PC and PMMA, having a relatively low viscosity, the PMMA content at the surface of the injection-molded plate is found to be dependent upon the temperature in the barrel. At the low barrel temperature, PMMA localizes at the surface, which is detected by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements at the surface and cross-section of the plate. The difference in the viscosity could be the origin of this phenomenon. Since the surface localization behavior significantly affects surface properties of molded products, this phenomenon is important to control the surface composition for this blend system.