This research work dedicated to studying the dielectric spectroscopy and the conduction mechanism of charge transport of $\alpha$-sexithiophene ($\alpha$-6T) thin film. $\alpha$-6T nanoparticles thin films were synthesized by the thermal evaporation technique. Both X-ray diffraction pattern and transmission electron microscopy show the polycrystalline nature of as-deposited $\alpha$-6T thin film embedded in the amorphous background with typical nanostructured. The dielectric constant ($\varepsilon'$), dielectric loss ($\varepsilon''$) and ac conductivity ($\sigma_{ac}$) measured as a function of frequency at different temperatures. The ac conductivity obtained by Jonscher’s universal law. The $\sigma_{ac}$ controlled by both the correlated barrier hopping (CBH) and well-localized hopping model. The increments of frequencies from 0.5 KHz to 20 KHz cause the influence on the values of the ac activation energy, where it decreased from 0.219 eV to 0.070 eV. The value of relaxation time ($\tau_0 = 4.545 \times 10^{-7}$ s) indicated that polarization occurs due to orientational polarization.