The improvement of oil transformer performance is related to several factors. The most important factors are dielectric and thermal capability. Nanotechnology is an effective science used for enhancing the dielectric and thermal properties of the transformer oil. In this work, barium titanate (BT) nanoparticles were dispersed into the pure transformer oil by 0.005 g/L volume fraction (vf%). From the obtained results, it is noticed that BT enhances the thermal properties of the transformer oil by about 33%, although, the dielectric properties were decreased by about 10%. To improve the dielectric properties also, 0.01 vf% titanium dioxide (TiO2) nanoparticles with 0.005 vf% BT was dispersed into the base oil. The hybrid nanofluid sample achieves about 33% and 45% enhancement for the thermal and dielectric properties, respectively.