In the paper, the effect of temperature (range 22 – 140 °C) on the power factor (PF) of composite material made of multi-walled carbon nanotubes with a 10 nm thick polyaniline coating applied to their surface has been studied. The conductivity value of the coating was varied by treating the composite with buffer solutions of different pH values. The nanotubes were randomly oriented relative to each other in the composite samples under study. It was found that the composite material where polyaniline was in an oxidized conductive form had the highest PF value. In that sample, the PF values were about 0.5 μW/(m∙K2) at room temperature and about 1 μW/(m∙K2) at 140 °C.