Semiconductor nanorods and nanowires are interesting nanomaterials and have been applied in sensor and energy applications. Tellurium is a typical p-type semiconductor having bandgap energy of 0.35 eV and has already been recognized as an interesting material for fabricating nanodevices. For examples, tellurium nanowires have shown great potential in the applications of nanogenerators, supercapacitor, lithium battery, and biosensors. In this paper, we developed a thin, light-weight, and flexible thermoelectric nanogenerator based on the nanocomposite of tellurium nanowire arrays and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The Seebeck coefficient of the nanocomposite was determined to be 235 μV/K. A linear relationship between the output voltage and the temperature difference across the thermoelectric nanogenerator was observed. We demonstrated that the thermoelectric nanogenerator can be integrated with fiber fabric and harvested the thermal energy from human body temperature. Not only for the purpose of energy harvesting, the thermoelectric nanogenerator can also function as a self-powered sensor for water temperature measurement.