The aim of this study was to obtain an effective compatibilizer for the blends of polylactic (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). PLA-polyethylene glycol-PLA (PLA-PEG-PLA) tri-block copolymers with different chain lengths were synthesized to emulsify the interfacial layer and improve the interfacial adhesion of PLA/PBAT blends. The structure of the tri-block was characterized, and the compatibilization effect was examined based on the microstructures and the thermodynamic, mechanical, and rheological properties of the blends. The tri-block copolymers exhibited attractive compatibilizing efficiency for PLA/PBAT blends when the segment ratio of ethylene glycol/lactic was 2.1. The elongation of the blends with the compatibilizer was as high as 173.4%, eight times more than the pristine blends. Moreover, there were typical sea-island microstructure changes to the continuous phase, and thread-like fibers appeared in the tensile-fracture images. The experimental results established that the PLA-PEG-PLA tri-block copolymers can act as an effective compatibilizer for PLA/PBAT blends to improve the interaction of the interface. (C) 2018 Elsevier Ltd. All rights reserved.