The miscibility of the blends of polycarbonate (PC) and syndiotactic polystyrene (s-PS) was investigated by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The blends exhibit two different glass transition temperatures ($T_g$) close to those of the pure components, indicating immiscibility at the melt mixing temperature of $280^{circ}C$. Morphological studies of the blends shows large dispersed particles and significant cavities between the matrix and the dispersed phase, especially for the PC matrix blends. To reduce such detrimental effects, poly(methyl methacrylate) (PMMA) or styrene-maleic anhydride copolymer (SMA) was added as a compatibilizer to the PC/s-PS blends. Both polymers contribute to enhancing the interfacial adhesion between PC and s-PS and reduce the particle size of the dispersed phase. Especially when PMMA was added, morphological studies showed that PMMA encapsulates the dispersed s-PS phase in the PC matrix. The elastic modulus of the PC/s-PS blend increased on adding PMMA or SMA, mainly because of enhanced interfacial adhesion. The pencil hardness of PC increased at least three times from that of neat PC as a result of compatibilization and surface enrichment of the s-PS phase, whose surface tension is lower than that of PC.