The compatibilizing effect of styrene-sodium methacrylate (S-NaMA) ionomer on nylon-6 (N6) and polystyrene (PS) blends was studied. The dispersed particle size of these blends containing the ionomers was significantly reduced compared with that of the blends without the ionomer. The reduction of the particle size was more pronounced when the ionomer with lower ionic content was added to the blend. The blends using ionomer with the lower ionic content showed higher tensile strength than the blends using ionomer with the higher ionic content. It is suggested that these results are caused by the proper combination of specific interactions and structural similarity between the component polymers and the ionomers.