An effective approach for improving dispersion states of multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) was employed via hybrid inclusion of the nanofillers in polyurethane matrix to further enhance viscoelastic properties. Nanocomposites based on MWCNTs, two groups of graphene and hybrid MWCNT/graphene with varied weight fractions and ratios were fabricated via a facile and scalable approach. Dynamic mechanical analysis results indicated an improvement of up to 86% in storage modulus at 25 degrees C for hybrid MWCNT/GNP-S750 at only 0.25 wt% loading, whereas solely MWCNTs and graphene nanocomposites showed 9% and 15% enhancement at the same content, respectively. The glass transition temperature value was enhanced by about 9.5 degrees C with 0.25 wt% inclusion of well-dispersed three-dimensional MWCNT/GNP-S750 structure, which disclosed a noticeable synergistic effect in thermomechanical properties. The reinforcement coefficient, adhesion factor, reinforcement efficiency factor, degree of entanglement and cross-link density of nanocomposites were also examined to evaluate the interaction of single and hybrid carbon nanofillers with PU matrix.