Over the past decades, emerging bioplastics have attracted much interest from the scientific and industrial communities because of public concerns about environmental problems and sustainable development. In this study, poly(lactic acid) (PLA) was toughened by ductile biodegradable poly(butylene adipate-co-terephthalate) (PBAT) and biosourced plasticizer epoxidized linseed oil (ELO), and a chain-extending agent (CEA) was added to promote the compatibility and toughness of the bio-blends. It was shown that "in situ" grafted polymers were created in the bio-blends with the aid of CEA, greatly enhancing the compatibility and ductility of the compatibilized blends. "In situ" grafted polymers remarkably increased the melt elasticity and viscosity of PLA/PBAT/CEA and PLA/PBAT/ELO/CEA bio-blends. The "in situ" grafts also improved the hydrophobicity and thermostability of the blends. However, the grafts disturbed the melting crystallization ability of the bio-blends. Owing to the synergistic effect of ELO and CEA, the tensile strain at break and Charpy notched impact strength of the PLA/PBAT/ELO/CEA (63/27/10/1) blend attained to 286 % and 52.53 kJ/m