The purpose of this work is twofold: the manufacturing of functionalized graphene (f-GNF) epoxy nanocomposite and time-dependent thermomechanical characterization of epoxy and nanocomposite. To accomplish these purposes, f-GNF-epoxy nanocomposites are produced for two different graphene fractions (0.1 and 0.5 wt%) using the non-covalent functionalization and three roll milling (3RM) dispersion techniques. Dynamic Mechanical Analysis (DMA) is performed to determine temperature-dependent viscoelastic properties. Quasi-static compression, creep and relaxation tests are conducted at two different temperature values: 65°C and 120°C. As expected, experimental results revealed that the elasticity modulus and yield stress decrease with increasing temperature. It is also determined that the reinforcing effect of graphene reduces with increasing temperature. An important conclusion revealed, through the compression, creep, and relaxation test results that graphene has no reinforcing effect at 120°C but has a weakening effect on total thermo-mechanical behavior.