Biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends and films were prepared by melt blending and blowing films technique in the presence of chain extender. The Joncryl ADR-4370F (ADR) was used as the chain extender. The effect of ADR on the mechanical properties, rheological behavior, morphology, and thermal behavior of PLA/PBAT blends was investigated. The mechanical properties were markedly improved by incorporation of 0.15 phr ADR, for example, the elongation at break increased from 23.5% to 410.3% and the notched Izod impact strength increased from 7.5 to 33.4 KJ/m(2) for the PLA/PBAT/ADR blends. The elongation at break increased from 17.7% to 264.6% and the tensile strength increased from 28.0 to 40.7 MPa for the PLA/PBAT/ADR films in the transverse direction. The tensile strength and tear strength of the films increased from 28.0 to 40.7 MPa and from 135.5 to 163.8 kN/m in the machine direction, respectively. Morphological observation through scanning electron microscopy revealed that the compatibility of the PLA/PBAT blends was greatly enhanced by the incorporation of ADR. The interfacial adhesion was improved between PLA phase and PBAT phase. These findings contributed new knowledge to the additives area and gave important implications for manufacturing biodegradable polymer packaging material. POLYM. ENG. SCI., 58:1868-1878, 2018. (c) 2017 Society of Plastics Engineers