The use of biodegradable polymers to mitigate the environmental pollution is one of the hot topics of research in the recent years. The current work presents the graphene oxide (GO) nanoparticles functionalized with two types of alkylamines (decylamine (DA) and octadecylamine (ODA)) synthesized at two different temperatures; 25 °C (GODA1 and GOODA1) and 80 °C (GODA2 and GOODA2), which were used as fillers to prepare PLA nanocomposites and their barrier, mechanical, and thermal properties were studied. The elemental analysis showed 2 wt% to 4 wt% of nitrogen content for functionalized GO, confirming the presence of alkyl chains in its structure. The reactions carried out at 80 °C (GODA2 and GOODA2) are the ones that showed the highest mass yields, registering a 7% and 50% increase in the total mass, respectively. These results were supported by X-ray diffraction (XRD), FT-IR spectroscopy and thermogravimetric Analysis (TGA) analyses. The optical microscopy images of the nanocomposites showed that the modified GO has a higher affinity than the GO with the PLA matrix, observing good dispersion at low loads of modified GO (0.2 wt%), with an increasing tendency to form agglomerates for higher loads. Furthermore, the elastic modulus of all nanocomposites showed a decreasing trend, mainly attributed to the formation of agglomerates and the decrease in the crystallinity of the composites. The oxygen permeability progressively decreases with increasing nanoparticle load, the nanocomposites prepared with GODA2 and GOODA2 presented the best results, registering decreases of 28.6% and 30.4% for 2 wt% loads, respectively. On the other hand, the permeability to water vapor decreased by 36.0% and 50.2%, for loads of 0.2 wt% of GODA2 and GOODA2, respectively. However, for higher amount of filler no significant improvements was detected. The results shows that the addition of modified GO to PLA improves its barrier properties, and that its composites could be used in food packaging.