Poly(ethylene 2,5-furan dicarboxylate) (PEF) is considered the biobased counterpart of the fossil based poly(ethylene terephthalate) for food packaging. In this research, PEF nanocomposites containing 2.5 wt% neat multi walled carbon nanotubes (MWCNTs), or functionalized MWCNTs or graphene oxide (GO), were in situ prepared by applying the melt polycondensation method. The nanocomposites showed faster crystallization rates compared to the pristine material as proved by both differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The latter evidenced an increased nucleation density in nanocomposites, due to the nucleating efficiency of the fillers, resulting in smaller spherulite size. However, a slightly reduced thermal stability was revealed for the nanocomposites by thermog-ravimetric analysis (TGA), especially in the case of GO-containing samples. The solid structure of the materials was studied by performing real time X-ray diffraction (XRD) measurements. In neat PEF, beta-crystals were observed in the solvent treated sample, while alpha-crystals were formed on cooling from the melt or cold-crystallization. On the contrary, in the XRD patterns of the nanocomposites only peaks associated with the alpha-crystal phase were found. Last, but not least, the effect of recrystallization on the thermal behavior was evaluated by means of modulated temperature DSC (MDSC). (C) 2016 Elsevier Ltd. All rights reserved.