Multiwalled carbon nanotube/poly(3-hexylthiophene) (MWCNT/P3HT) composites were prepared by oxidative polymerization of 3-hexylthiophene in a MWCNTs dispersed chloroform solution. The phase composition of the composite materials was analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The thermoelectric properties of the composite powders, after cold pressing into pellets, were measured at temperatures between 293 and 423K. The electrical conductivity of samples containing 30wt% MWCNT displayed a gradual decrease in conductivity from 0.13 to 0.11S/cm across this temperature range and was accompanied by an increased in the Seebeck coefficient from 9.7 to 11.3μV/K.