The effect of pre-sintering temperature on the activation energies of dc and ac conduction in sol-gel spin-coated Ba0.5Sr0.5TiO3 (BST) thin films is reported in this paper. Layer by layer coating of BST sol on Pt/TiN/SiO2/Si substrates was done with varying pre-sintering temperatures (drying temperature for individual layers). Dominant mechanism of dc conduction was identified as Schottky process whereas ac conduction was governed by trap controlled hopping process. The activation energy for dc conduction decreased from 0.45 to 0.38 eV with increase in the pre-sintering temperature from 400 to 600 °C; whereas, that for ac conduction increased from 0.17 to 0.21 eV. The results have been correlated with grain growth phenomena and reduction of oxygen vacancies in the films with increase in the pre-sintering temperature. © 2006.