Development of high performance multi-component immiscible polymer blends and recycling and reusing scrap or waste plastics have been difficult because of the difficulty of compatibilization, especially the preparation of an effective compatibilizer for such blends. Here we present a novel and effective strategy to compatibilize three immiscible polymers, polyolefins, styrene polymers, and engineering plastics, achieved by using a polyolefin based multi-phase compatibilizer. Compatibilizing effect and morphology development were investigated in a model ternary immiscible polymer blends consisting of polypropylene (PP)/polystyrene(PS)/polyamide(PA6) and a multi-phase compatibilizer. The results show that, as a multi-phase compatibilizer, (PP-g-(MAH-co-St) exhibits strong compatibilization in the above immiscible blends, as demonstrated by the improved tensile and impact properties, finer dispersion of the PS and PA6 phase, and increased interfacial adhesion. This work provides a novel strategy not only for developing ternary or multi-components polymer blends with unique performance, but also useful for recycling and reusing three immiscible polymers, polyolefins, styrene polymers, and engineering plastics from the waste stream.