Polythiophene and Nickel nanoparticles were synthesized by chemical oxidation and modified polyol methods respectively. Both powders were mixed mechanically in different weight percentages and the composites were prepared. Dielectric properties for pure PTh and PTh-Ni nanocomposites have been measured as a function of frequency in the range from 1 kHz to 1 MHz and temperature in the range from 303 K to 473 K. Dielectric constant and dielectric loss both decreased with increase in frequency and increased with increase in temperature. Conductivity has been determined using dielectric data and all the samples have shown semiconducting nature. Intersecting frequency between real and imaginary parts of dielectric constant has been determined and its variation with temperature was analyzed. Motts SPH model has been fit to the conductivity data and activation energy has been calculated. Activation energy for ac conduction decreased with increase in frequency and Ni content.