The addition of nanoparticles into a polymer can produce multifunctional films having not only gas barrier and antimicrobial characteristics for active packaging, but also improved mechanical and thermal behaviours. Among the different nanoparticles, graphene oxide (GO) has the potential to develope active polymers due to its layer structure and biocide property. In this study, linear low density polyethylene (LLDPE) was melt mixed with GO nanoparticles having different oxidation and exfoliation degrees. Our results shown that the elastic modulus of LLDPE composites increased with the amount of GO, and by using highly oxidated GO this reinforcement effect was observed without reducing the elongation at break. The thermal stability of the composites under either inert and oxygen atmosphere also increased as compared with the pure matrix. Regarding the barrier properties, the oxygen permeability of the composites depended on the amount and kind of filler, and while GO with low oxidation increased dramatically the permeability of the polymer, highly oxidated GO decreased this value. These results were explained through the Felske model. Water vapor permeation otherwise was not affected by the presence of the nanofillers. The LLDPE/GO nanocomposites further presented antimicrobial behaviour against Salmonella Typhi and Listeria monocytogenes strains. These results confirmed that GO can be designed as an active filler in polymer nanocomposites for packaging applications.