This work provides a detailed information on the preparation process and characterization of functionalized multiwalled carbon nanotubes/Epidian 6 nanocomposites using ARES rheometer, TGA, and DSC measurements, with the imidazole derivative as a curing agent. Scanning electron microscopy of the fracture surfaces of the composites with a total nanofiller concentration below 0.5 wt.% reveals a uniform dispersion of MWCNT with only some minor agglomerates. At the same time, the TEM analysis of the composite with a total concentration of MWCNT-COOH higher than 0.5 wt.% confirmed the presence of carbon nanotube aggregates along with a large number of places without any presence of nanoparticles in the whole volume of the epoxy matrix. Mechanical tests (bending as well as dynamic mechanical analysis) show that compared with the neat epoxy resin, the bending strength of the composite was improved by about 30 and 21% after incorporating as little as only 0.1 and 0.2 wt.% MWCNT-COOH, respectively. The work presented hereby is a continuation of a previous study on epoxy-based nanocomposites with different types of multiwalled carbon nanotubes and it is a part of a wider project on precise charting of the influence of carbon nanotubes (particularly multiwalled carbon nanotubes) in the system of epoxy resin with 1-buthylimidazole, as a curing agent.