The effect of hydrogen on 120o<111> twin boundaries in γ phase of an as-cast and as-forged Ti–46Al–2V–1Cr–0.3Ni alloy was investigated by means of annealing treatment in hydrogen atmosphere, and the microstructure was observed by an optical microscopy, a scanning electron microscopy, an electron back scattered diffraction technique, a transmission electron microscopy and a X-ray diffraction apparatus. The results showed that hydrogen could promote γ-phase static recrystallization of the as-cast and as-forged alloy, and the extent of static recrystallization increased with increasing hydrogen content. Many static recrystallization grains possessed 120o<111> twin boundaries. The relationship between the fraction of 120o<111> twin boundaries and hydrogen content was given. Hydrogen-weakened γ-phase elastic anisotropy increased 120o<111> twin boundaries.