Poly(ethylene terephthalate) (PET) resin is one of the most widely used thermoplastics, especially in packaging. Because thermal and hydrolytic degradations, recycled PET (RPET) exhibits poor mechanical properties and lacks moldability. The effects of adding elastomeric modifiers, chain extenders (CE), and poly(butylene adipate-co-terephthalate), PBAT, as a toughener to RPET on its moldability and mechanical property were investigated. Melt blending of RPET with CE, thermoplastic elastomer (TPE), and/or PBAT was performed in a thermokinetic mixer (K-mixer). The blended materials were then injection molded to produce tensile specimens. Various techniques were used to study the mechanical properties, rheological properties, compatibility, and crystallization behavior of the RPET blends. By melt blending with proper additives, recycled PET regained its moldability, thereby enabling the recycling of RPET. Furthermore, the addition of CE greatly enhanced the mechanical properties of RPET. While the RPET and TPE blends also showed improved mechanical properties, the improvement was less significant and the blends were often immiscible due to the difference in polarities between RPET and TPE. Finally, it was found that the mechanical properties of RPET blends depended on the prior thermal history of the material and could be improved with an extra annealing step that increased the degree of crystallinity. POLYM. ENG. SCI., 51: 1023-1032, 2011. (C) 2011 Society of Plastics Engineers