We report on a study of the effects on the thermoelectric properties of CNT films of incorporating Au nanoparticles of different sizes. Our characterization included measurements of the electrical conductivity, thermal conductivity, and Seebeck coefficient, as well as estimation of the power factor and dimensionless thermoelectric figure of merit for these materials. We found that the thermoelectric properties were significantly affected by the size of Au-nanoparticles used. Addition of Au-nanoparticles of both small (~5nm) and large (~60nm) diameters led to a decrease in the electrical conductivity from 1.8×10 5 Sm −1 for the pure CNT film to 6.2×10 4 and 7.9×10 4 Sm −1 for samples functionalized with 5nm and 60nm Au-NPs, respectively. Addition of 5nm Au-nanoparticles also led to a decrease in the thermal conductivity to 73Wm −1 K −1 from 82Wm −1 K −1 for the pure CNT film, whereas the thermal conductivity of the sample with 60nm Au-nanoparticles increased to 106Wm −1 K −1 . The pure CNT film had a Seebeck coefficient of 31μVK −1 , while the samples with 5 and 60nm Au-NPs only achieved ~25μVK −1 . The best value for the thermoelectric figure of merit (ZT) was 6.04×10 −4 for the pure CNT film, and 1.73×10 −4 and 1.33×10 −4 for the samples with 5nm and 60nm Au-NPs. The power factors were found to be 1.67×10 −4 , 4.2×10 −5 , and 4.7×10 −5 Wm −1 K −2 for the pure CNT, and the samples with 5 and 60nm Au-NPs, respectively.