Electrical breakdown phenomena of barium titanate ceramic were studied. Sintered ceramic samples made from high purity BaTiO ₃ powders with varying particle sizes were obtained by heat treatment in the range of 1280∼1400°C. The resulting average grain size value changed from 1.3 μ m to over 40 μ m. After applying gold electrodes, electrical breakdown test was performed at two different temperatures, i.e. room temperature and 150°C, for samples immersed in silicone oil bath using 60 kV dc power supply with voltage rate of 500 V/s. As a consequence, both intrinsic and extrinsic failure mechanisms were identified and commonly occurred in these materials. Effects of sample thickness and grain size on breakdown strength are discussed in some details. Crystalline state, i.e. either ferroelectric tetragonal phase or paraelectric cubic phase, showed great influence on intrinsic breakdown mode. A qualitative model for intergranular and transgranular mechanisms is proposed.