It is shown by differential scanning calorimetry (DSC) measurements that Lightly sulfonated polystyrene (SPS) is partially miscible with polysulfone (PSF), polycarbonate (PC), polyetherimide (PEI), and a thermotropic liquid crystalline polymer (LCP). Fourier transform infrared analysis confirms that the miscibility of SPS and PSF, and of SPS and PC, comes from the ion-dipole interaction between the sulfonate groups of SPS and the polar groups of PSF and PC, respectively. After the addition of SPS to LCP/PSF, LCP/PC, and LCP/PEI blends, this specific interaction leads to the compatibilization of SPS in these blends, which is revealed by inward glass transition temperature shifts of component polymers in DSC and dynamic mechanical analysis thermograms and by a much finer dispersion of the minor LCP phase in these matrix polymers. The utilization of SPS as the compatibilizer results in a stronger interfacial adhesion between LCP and matrix phases and improves the mechanical performances of LCP/PSF, LCP/PC, and LCP/PEI blends as well. Compared with ternary LCP/PSF, LCP/PC, and LCP/PEI blends with polystyrene as an inert third component, the ternary LCP/SPS/PSF, LCP/SPS/PC, and LCP/SPS/PEI blends have significantly enhanced tensile strengths and moduli, with acceptable processabilities at the same time.