CdTe films were deposited at different substrate temperatures (423-573 K) using the hot wall evaporation technique. The films were polycrystalline in nature with varying grain size (0.06-0.18 mu m) Dark and photo-conductivities in the films were measured in the temperature range 90-300 K. The conductivity data at low temperatures (< 155 K) were analysed by using the quantum mechanical tunnelling of carrier through the grain boundary barrier model. The relatively large conductivity at the higher temperature region (> 155 K) was explained by the possible thermionic emission of the carrier over the grain boundary potential barrier. The influence of the modulated grain boundary barrier height (at high temperature) and width (at low temperature) with different illumination levels could explain the overall conductivity of CdTe films.