The miscibility and properties of the alloys composed of polyphenylene ether (PPE), polystyrene (PS), and acrylonitrile-styrene (SAN) polymers have been studied. The heat distortion temperature and flexual strength decreased with increasing AN contents in SAN in PPE/SAN alloys because the mutual solubility was poor in the high-AN content region. However, PPE/PS/SAN alloys showed higher heat distortion temperature and higher flexural strength than the PPE/PS miscible alloy and the PPE/SAN immiscible alloy. Furthermore, the PPE/PS/SAN alloy has excellent fluidity. It is a kind of immiscible alloy without a compatibilizer, which shows the excellent properties. The results suggested that there is a so-called "entanglement phase" between two separated phases and PPE distributed to both phases, and this phase is superior to that in which compatibilizer was added to enhance miscibility. Moreover, it is very useful for recycling materials because it does not contain a sophisticated compatibilizer.