In order to preserve the life time of oil transformers and to improve their performance, the transformer oil must play its role as insulating and cooling medium efficiently. Nanotechnology is an effective science used for improving the dielectric and thermal properties of the transformer oil. In this paper, barium titanate (BT) nanoparticles were mixed with the neat insulating oil by 0.01 g/L and 0.02 g/L concentration. Breakdown voltage and heat transfer coefficient were measured to excogitate the transformer oil dielectric and thermal properties, respectively. From the obtained results, for 0.01 g/L sample, it is noticed that BT enhances the thermal properties of the transformer oil by about 28.3% but, the dielectric properties were slightly increase by about 2%. The increasing of the BT nanoparticles concentration to 0.02 g/L achieves unsatisfied results due to the agglomeration and the sedimentation of BT particles into the oil.