The present study focuses on the design of new nanocomposite films using bio-based thermoplastic polyurethane (TPU) as a polymer matrix and long chain amine functionalized reduced graphene oxide (G-ODA) as a nanofiller. G-ODA was successfully prepared via chemical grafting of octadecylamine and fully characterized by various physicochemical techniques. Dispersion experiments showed that the synthesized organophilic graphene could be easily dispersed in several organic solvents and forms a stable and homogeneous colloidal suspension. G-ODA was incorporated at different loadings (0.1, 0.3, 0.5 and 0.7 wt%) into the polyurethane (PU) matrix to prepare uniformly dispersed G-ODA based PU nanocomposites. The designated nanocomposites resulted in achieving enhanced thermal stabilities as well as excellent mechanical properties compared to the neat PU. Mechanical performance studies show a tremendous enhancement of the tensile strength (2.08 to 5.48 MPa) along with an increment of the tensile modulus (37.19 to 122.83 MPa), the elongation at break (9.67 to 28.91%) and the toughness (13.75 to 124.44 MJ m⁻³). In addition, the designed nanocomposites demonstrate limited moisture and water uptake, reduced permeability and enhanced surface hydrophobicity.