We studied the phase transition behavior of cubic BaZrO3 perovskite by in situ high pressure synchrotron X-ray diffraction experiments up to 46.4GPa at room temperature. The phase transition from cubic phase to tetragonal phase was observed in BaZrO3 for the first time, which takes place at 17.2GPa. A bulk modulus 189 (26) GPa for cubic BaZrO3 is derived from the pressure-volume data. Upon decompression, the high pressure phase transforms into the initial cubic phase. It is suggested that the unstable phonon mode caused by the rotation of oxygen octahedra plays a crucial role in the high pressure phase transition behavior of BaZrO3. (C) 2014 AIP Publishing LLC.