The effect of zinc oxide (ZnO) on the morphology and mechanical properties of poly(styrene-coacrylonitrile)(SAN) and poly(methyl methacrylate) (PMMA) blends was investigated. Composites ofblends of SAN and PMMA (20/80 wt%) with ZnO were prepared by melt mixing in a twin screwextruder and then the composites were molded by compression molding method. The dispersion ofZnO particles in the matrix polymers was investigated using SEM. It was observed that the dispersionof ZnO particles was relatively good with low ZnO content but the aggregates of ZnO particles in apolymer matrix increased with increasing ZnO content. The mechanical test showed that the tensilestrength and stress at break of SAN/PMMA blends decreased slightly with increasing ZnO content.Increasing content of ZnO up to 1.0 wt% increasing the Young’s modulus and impact strength ofSAN/PMMA blends while the addition of ZnO beyond 1.0 wt% decreased the Young’s modulus andimpact strength.