Compatibilized poly(ether imide)/amorphous polyamide (PEI/a-PA) blends were obtained in the melt state by substitution of 20% PEI by poly(ethylene terephthalate), PET. The two amorphous phases of the blends comprised both a miscibilized 80/20 PEI/PET blend and an a-PA-rich phase in which small amounts of PET and probably PEI were present. The presence of PET in the two phases of most of the blends was the main reason for the clear decrease in the particle size that indicated compatibilization. The smaller interfacial tension of the blends after PET addition also proved that compatibilization had occurred. The deviation of the modulus with respect to the direct rule of mixtures was positive in PEI-rich blends and negative in the blends very rich in a-PA. The modulus values were tentatively attributed to a different orientation of the components of the blends in the blends and in the neat state. The clear increases in ductility and the impact strength after PET addition further demonstrated the compatibilization effect of PET.