Nanocomposites based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) copolymers of different hard to soft segment ratios (40:60 and 60:40) and three different carbon nanofillers of different aspect ratios (dimensions), as 0D carbon black, 1D multiwalled carbon nanotubes, and 2D graphene, have been prepared in situduring two-stage polymerization. FTIR and NMR spectroscopy was used to characterize the chemical structures of the obtained nanocomposites. Scanning electron microscopy (SEM) indicated very good dispersions of all carbon nanofillers in both polymer matrices. DSC results revealed that the addition of nano-sized fillers eliminated cold crystallization of materials containing 40% hard segments in polymer matrix. We found that the high aspect ratio, 1D nano-filler (multiwalled carbon nanotubes) strongly nucleated crystallization of materials containing 60% of hard segments. This nanofiller also yielded the greatest improvement in the Young’s modulus as assessed by tensile tests, both at 24 ºC and 37 ºC. On the other hand, for nanocomposites containing 2D nanofiller (graphene) we observed reduced bacterial adhesion. Finally, in vitro cytocompatibility tests with L929 murine fibroblasts demonstrated cell growth on all materials except nanocomposites containing carbon nanotubes, where the lowest fibroblast viability was observed.