Various particle sizes of starting barium titanate were used to investigate the effect of external pressure and grain size on the phase transition in the Gd-doped BaTiO3 ceramic. The particle size of starting BaTiO3 was somewhat proportional to the grain size, while internal stress is inversely related to the grain size. Grain size refinement as well as external pressure shifts T-c to a lower temperature, whereas orthorhombic-to-rhombohedral T-2 shifts to a higher temperature. The tetragonal-to-orthorhombic T-1 decreases with increase in pressure, reaches a minimum value, and then increases.