The blends of polyarylate (PAR) / polycaprolactone(PCL) or PAR / poly(ethylene adipate) (PEA) showed two separate Tg''s, a sign of phase separation, but the partial miscibility viewed from the thermal properties and crystallization behaviors was large. From the morphologies. the compatibilizing effect of PEA in PAR / poly (styrene-co-acrylonitrile) (SAN) blend was observed. The degree of phase separation in PAR / SAN / PEA system was reduced by staying at high temperatures. This phenomenon was thought to be due to the transesterification reaction of PAR and PEA and the improved compatibilizing effect of copolymer obtained from the transesterification reaction. With the transesterification reaction, the PAR-rich phase dissolved into the SAN-rich phase until a homogeneous phase formed, which was more evident at the higher temperature, at the lower PAR / SAN weight ratio, and at the higher content of PEA in the blend.