Nanocomposites based on the tetraglycidyl methylene dianiline (TGMDA) epoxy resin using various kinds of nanofillers such as multiwalled carbon nanotubes (MWCNT) (1D filler) and graphene-based nanofillers (2D filler) are investigated in this paper. The 4,4-diaminodiphenyl sulfone (DDS) is used as curing agent. Despite very good mechanical performance of the TGMDA epoxy resin, one of the current limitations of this epoxy precursor is related to the high value of the viscosity. In order to optimize the dispersion of the nanofillers inside the epoxy-DDS mixture we have fluidified the initial epoxy precursor with an epoxy reactive monomer which has proven to be very effective to lower the viscosity of the nanoparticles/resin mixture and therefore in facilitating the nanofiller dispersion step. In this work the rheological properties of MWCNT/epoxy nanocomposites and of graphene/epoxy nanocomposites filled with two similar graphene-based nanofillers, differing essentially for the exfoliation degree and for the content of carboxylated groups, are investigated in the liquid state (with the inclusion of DDS) before curing. The rheological measurements were carried out on a Physica-MCR301 (Anton-Paar) rotational rheometer equipped with a parallel plate geometry. Small amplitude oscillatory shear measurements, within the linear viscoelasticity regime, on the liquid mixtures with different contents of MWCNT and graphene-based nanoparticles were performed at different temperatures. Dynamic mechanical properties of the cured samples were performed with a dynamic mechanical thermo-analyzer (Tritec2000 DMA-Triton Technology). Thermal analysis has been used to study the oxidative stability of the components and the formulated resins. The effect of CNTs and graphene-based nanoparticles on the thermogravimetric curves has also been analyzed in this paper.