The influence of the component ratio in the stabilized binary blends of amorphous polycarbonate (PC) and polyethylene terephthalate glycol (PET-G) on the compatibility of components, relaxation, rheological and mechanical properties was studied. The materials were prepared by reactive mixing of the components in the melt in a mixing rectifier based on a twin-screw extruder with unidirectional screw rotation. It is established that the components in the blends are mutually soluble over the entire range of their concentrations. The temperature of the а -process of relaxation (the glass transition temperature, Tg, in the mixtures) is in the interval between the values of Tg PC = 148.3 °C, Tg PET-G = 82.0 °C and obeys the Fox equation for single-phase blends. The mechanical characteristics of the mixtures change in a non-additive way when the concentration of the components is varied. In particular, in blends in which the PC content prevails, a significant increase in the upper yield limit is observed in comparison with the additive values, which, according to the relaxation spectrometry, is due to intense intermolecular interactions.