Polyaniline (PANI), Graphene Oxide (GO) and PANI-GO nanocomposite were prepared using in-situ polymerization and Hummer's method. GO can improve the thermoelectric properties (TE) of polyaniline by varying the concentration of GO. The morphological and structural studies confirm the uniform growth of PANI on the surface of GO during polymerization and leading to an order crystalline structure in amorphous matrix. Raman analysis and Fourier transform infrared spectroscopy (FTIR) studies shows strong pi-pi interaction of PANI over the surface of GO. And other interactions such as hydrogen bonding and electrostatic interaction between PANI and GO gives good support to increase their TE properties. The TE properties of PANI and PANI-GO nanocomposite have been investigated in the temperature range of 298 to 363 K. The electrical conductivity, Seebeck co-efficient and power factor of the sample PG2 (20% GO) is around 1489 S/cm, 59 mu V/K and 52.11 10(-7)W/K-2 cm at room temperature (RT), which is 1.2 times, 1.15 times and 1.5 times higher than pure polyaniline. And the sample PG2 (20% GO) showed the highest ZT at 363 K of 0.8 and at room temperature 0.4, which is 1.25 times and 1.23 times higher than sample PP.