The single enhancement of cellulose nanosphere (CNS) can improve crystallization and mechanical strength of poly(lactic acid) (PLA) by heterogeneous nucleation, even their poor compatibility. However, little attention is paid to the synergistic effects of interfacial interaction, nucleation and plasticizing to enhance the performances of PLA materials. The main objective of this work was to graft plasticizing poly(ethylene glycol) (PEG) with various chain lengths on CNS surface, and the effect of CNS-g-PEG and CNS on the PLA properties was compared. It is found that at the same loadings, the addition of CNS-gPEG showed a more positive effect on chain mobility, crystallinity, thermal stability, mechanical, barrier, and migration properties of PLA than CNS. Especially, simultaneous enhancements in strength and toughening were found for all the PLA/CNS-g-PEG nanocomposites, the strength and elongation at break for PLA/CNS-g-PEG6000 were increased by 101.4% and 431.7%, respectively. Meanwhile the water uptake and water vapor permeability of PLA/CNS-g-PEG2000 were reduced by 78.5% and 76.2%, respectively. This study suggests that green PLA nanocomposite films containing CNS-g-PEG nanofillers could be used as robust-barrier food packaging materials. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.