We determined the phase diagram and the equation of state (EoS) of TiH2 at high pressures up to 8.7GPa and high temperatures up to 600°C by in situ synchrotron radiation X-ray diffraction measurements. Compression induced strain inhibited the phase transition from the low-temperature bct phase to the high-temperature fcc phase, making the phase diagram difficult to determine. However, heating around 600°C relieved the strain, and the phase boundary between the bct and fcc phases was elucidated. The phase transition temperature at ambient pressure increased from around room temperature to 200°C at 8.7GPa. The high temperature Birch–Murnaghan EoS was determined for the fcc phase. With the pressure derivative of the bulk modulus K′0=4.0, the following parameters were obtained: ambient bulk modulus K0=97.7±0.2GPa, ambient unit cell of the fcc phase V0=88.57±0.02Å3, temperature derivative of the bulk modulus at constant pressure (∂K/∂T)P=−0.01±0.02, and volumetric thermal expansivity α=a+bT with a=2.62±1.4×10−5 and b=5.5±4.5×10−8. K0 of fcc TiH2 was close to those for pure Ti and bct TiH2 reported in previous studies.